[GMCnet] tranny kickdown switch

[Skip Hartline]

On my 74 Grand Canyons I found stuck behind the side console a bombardier switch tied to the kickdown switch on the gas pedal. I've heard of these, is there a corect procedure for using this where it doesn't scramble the tranny.
Skip
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[Ken Henderson]

Word from Manny and others is that kick-down is NOT a good idea.
Using the lever for S provides more hydraulic pressure to the bands
(or clutches?).

JWIH,

Ken H.

On Wed, Dec 21, 2011 at 2:52 PM, Skip Hartline wrote:
>
>
> On my 74 Grand Canyons I found stuck behind the side console a bombardier switch tied to the kickdown switch on the gas pedal. I've heard of these, is there a corect procedure for using this where it doesn't scramble the tranny.

[Skip Hartline]

Do mean "slow" when you say S

[Bob de Kruyff]

Ken Henderson wrote on Wed, 21 December 2011 13:02

I subscribe to both methods. If I'm climbing I'll pull the lever into 2 or 1 but it's still nice to have the kickdown switch operational for those quick passing or in town maneuvers.
--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Larry Davick]

I'd always thought it stood for Second. Park, Reverse, Neutral, Drive, Second, Low is what I always thought the PRNDSL stood for.

Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach

[Skip Hartline]

The dash has been replaced and it doesn't have an S

[J A Holland]

ljdavick wrote on Wed, 21 December 2011 14:20

~ NOPE ~ It Is None Of The Above ~

I Speak From Experience ~
Having Purchased A New 1956 Dodge D500 2 Door Hardtop,
with a HEMI and Push Button Powrtflite Tranny~
When I took my girlfriend for her 1st ride in it,
she asked about the buttons on the left side of the dash ~
SO
I EXPLAINED As Follows;

D ~> Is For DAY Driving ~

N ~ Is For NIGHT Driving ~

L ~ Is For LONG Trips ~

R ~ Is For RIGHT STRAIGHT AHEAD ~
{ and she believed me }

~ Joe ~

--
/_]*[__][] *[__|] ~ * '73 TZE063V101887 ""
O----------OO--]* ~ '78 TZE168V100234 ""
" Joe & Lavelle " ""
'sweet home alebamy'

[Skip Hartline]

We had a 56 plymouth savoy with the same tranny, when I was a KID, and they always told me the r was for race

[Terry Taylor]

I seem to remember from growing up with my dad, who was an
"Oldsmobile Man" (we had a 55 '88, and 61 and 63 "Dynamic
88"s) that the S stood for "Super" drive, Oldsmobile's term
for 2nd gear.

On 12/21/2011 12:20 PM, Larry Davick wrote:
> I'd always thought it stood for Second. Park, Reverse, Neutral, Drive, Second, Low is what I always thought the PRNDSL stood for.
>

[Skip Hartline]

Since we have fallen off the edge into the humorous side. I need to ask advise. The first part of the story is true. I went out to my pickup Sunday AM parked in the side yard and laid out by it was a beautiful 5x8 throw rug not a thing wrong with it other than damp from he dew. My question is do I call our commander in chief and tell him I've got an Iranian stealth drone that landed in my side yard and see if he could negotiate to get our's back from Iran. LOL

[Bob de Kruyff]

""I'd always thought it stood for Second. Park, Reverse, Neutral, Drive, Second, Low is what I always thought the PRNDSL stood for.

park, reverse, neutral, drive, super and low in this case

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Ken Henderson]

"S"uper = 2nd gear.

Ken H.

[Larry Davick]

Ken says "S"uper = 2nd gear.

I say "S"uper = "S"econd gear ;~)

Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach

_______________________________________________

[Larry Davick]

Dang! The owners manual says "S"uper too.

Just what I get for learning to drive in a Dodge.

Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach

----- Original Message -----
From: "Ken Henderson" <hend...@bellsouth.net>
To: gmc...@temp.gmcnet.org
Sent: Wednesday, December 21, 2011 2:33:53 PM
Subject: Re: [GMCnet] tranny kickdown switch

[brian]

it sure helps using "super" when you drive over the mountains.
for those of you who have not, you should, it will add to the respect level for the trans, it helps with the brakes too
--
brian
asheboro, nc
75 eleganza 2 74 build
118k miles and counting,
DOG HOUSE

[r...@gmcnet.org]

I unplugged my kick down and only pull it into super manually. My tranny has a shift kit in it so it shifts harder then stock. On a hill it down shifted OK but at times the up shift was too violent. I unplugged it to save the tranny from destroying itself.
--
Roy Keen
Minden,NV
76 X Glenbrook

[Johnny Bridges]

When we learnt though, the Dodge and Plynmouth had (in my not very humble opinion) the best automatic transmission ever constructed - the A727 TorqueFlite.  (And it's l'il brother the A929).  Ause the FordOMatic, it would break in half.  Abuse the TorqueFLite, it merely chirps the tires and keeps on shiftin'.  On my 340 car, it would break the tires and get sideays every time it shifted.  
 
--johnny
 
'76 23' transmode norris
'76 palm beach 

________________________________
From: Larry Davick <ljda...@comcast.net>
To: gmc...@temp.gmcnet.org
Sent: Wednesday, December 21, 2011 5:42 PM

[Greg and April]

All this talk about the tranny kickdown switch, has me wondering what
options there are for improving on the stock tranny - any thoughts?

.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

[Gary Casey]

In spite of how it feels during a full throttle upshift, I'm sure it will not "destroy itself."  However, downshifting from 3rd to second manually is significantly harder on the transmission than downshifting automatically by way of the detent ("kickdown") switch.  When downshifting manually the second overrun band is engaged and it will try to pull the engine up in speed.  When doing a full throttle automatic downshift the third clutch is simply released and the engine is merely allowed to increase in speed until the second freewheeling clutch engages - very gentle compared to trying to jerk the engine up with the second band.  The second gear band is very, very fragile and it doesn't take a lot of high speed downshifts to burn it up.  When I need to downshift I'll go to full throttle momentarily to trigger the downshift and then move the lever to the "S" position to hold it in second.  Avoid manually forcing the downshift unless it is really
necessary.  The upshift to third is no different whether selected manually or allowed to happen automatically. 

A manual 1-2 shift, however is a totally different animal.  When in either S or L the transmission line pressure is increased to the maximum - usually about 150 psi.  So the manual 1-2 shift, even if done at very light throttle, is done at maximum line pressure.  That can really jerk, but it still won't destroy the transmission.  One way to "trick" it:  With the transmission selector in L and the transmission in 1st, go to full throttle and immediately shift to D, back off a little on the throttle, allowing it to shift to second.  Immediately pull the lever back into S, holding it in second.

I've seen some "shift kits" that make logical changes in the shift calibration to speed up the shifts without making them too harsh.  But I've seen others where the builder seemed to think that if some is good a lot more is better.  These guys will often throw away check balls that are there to control shifts, leaving the clutches with no fill restrictions at all.  Just doesn't make sense.  And then they will increase the pressure regulator spring force to the point that the shifts are impossibly harsh.  Doesn't help the transmission, doesn't make it run cooler - all it does is make it obnoxious.

Just my opinion.
Gary Casey

I unplugged my kick down and only pull it into super manually. My tranny has a shift kit in it so it shifts harder then stock. On a hill it down shifted OK but at times the up shift was too violent. I unplugged it to save the tranny from destroying itself.
-- 
Roy Keen

[Bob de Kruyff]

Greg and April wrote on Wed, 21 December 2011 18:19

You need to be carefull about this net since you may get anxiety attacks if you take it all at face value. The THM 425 is as good as it gets. I would concentrate on maintaining it with regular oil changes and watch the temps if you can. Other than that, leave it alone. There's a distinct danger about "knowing too much" about the details. I have met many owners who have never read the net and blissfully enjoy the coaches to the limit.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[John R. Lebetski]

I'd leave the kickdown connected, as those engineer guys at GM designed it. You can still shift manually in demading situations, and I do. A bigger 'no no' is with it disconnected you can lug the engine (Dick P and Jim K and others will vouch for that being a "bad" thing) I'd rather have a touch more wear on the trans than lug the engine and have the MH not respond when trying to accelerate.
--
John Lebetski
Chicago, IL
77 Eleganza II

[Bob de Kruyff]

Gary, I think you are on the right track on that personally. I am constantly in the mountains here and although I still have the 3.07 with a heavy coach, I feel I have adequate ratio coverage and tend to shift as you describe. There are some inclines and declines where I just leave it in 1st or 2cnd and try not to shift at all. Revving the engine does not bother me a bit and if I can maintain a gear I would prefer that. The other thing I do that may not be recommended is leave it in L (1 first gear) and let the trans upshift and downshift by itself when it reaches it max shift rev limit. It's not very traumatic and on some of those mountain roads, I don't have time to be fooling with that "balky" shift lever. Unless modified, these transmissions will override the selector position to protect the engine and transmission and frankly the revs don't get that high.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Jim Kanomata]

Do not go with a shift kit on the transmission.
Majority of the shift kits increase the line pressure, which can cause
the torque converter to exert extra force forward the crank and wipe
out the thrust bearing and the crank.
Manny T. also mentioned this as well.

Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Greg and April]

I was just thinking that tranny tech, has come a heck of a long way since
the last GMC was built - to some extent I'm kind of surprised that something
better hasn't been developed.
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Bob de Kruyff" <NEXT...@AOL.COM>
To: <gmc...@temp.gmcnet.org>

[J A Holland]

Johnny Bridges wrote on Wed, 21 December 2011 18:57

> When we learnt though, the Dodge and Plynmouth had (in my not very humble opinion) the best automatic transmission ever constructed - the A727 TorqueFlite.  (And it's l'il brother the A929).  Ause the FordOMatic, it would break in half.  Abuse the TorqueFLite, it merely chirps the tires and keeps on shiftin'.  On my 340 car, it would break the tires and get sideays every time it shifted.  
>  
> --johnny
>  
> '76 23' transmode norris
> '76 palm beach 
>
>
> ________________________________

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The Indiana Toll Road was under construction when I purchased my '56 Dodge D-500
and it had a set of Goodyear Double Eagle Tubeless Tires on It ~
We wanted to drag race on the newly poured concrete roadway and went around
the construction barricades on the Tollroad between South Bend and Elkhart ~
Merv Miller lined up his '56 Chevy Bel Air against my '56 Dodge D-500 ~
When Nobie dropped the flag, The Goodyear Double Eagle Tubeless Tires
made contact with the Fresh Rough Cement Roadway and BOTH REAR TIRES WENT FLAT ~
I Broke The Seal, the Rims were spinning but the tires were not ~
We had to take both rear wheels off and to a Service Station For Air
The Station Attendant poured lighter fluid around the tire bead and lit it,
Then he put air in the tires abd the bead did not break again ~

~ Joe ~
--
/_]*[__][] *[__|] ~ * '73 TZE063V101887 ""
O----------OO--]* ~ '78 TZE168V100234 ""
" Joe & Lavelle " ""
'sweet home alebamy'

_______________________________________________

[Larry Davick]

It's the form factor. This case just isn't used in any modern vehicles, and there aren't any modern transmissions that would easily fall in to the hole. Believe me there would be great interest in a modern 6 speed.

Larry Davick

[Bob de Kruyff]

""I was just thinking that tranny tech, has come a heck of a long way since
the last GMC was built - to some extent I'm kind of surprised that something
better hasn't been developed.
""

Most of the newer tech involves electronic controls and integration with engine and other vehicle functions. For a torque converter planetary style like ours, very little has changed. Our design is a premium design that many still use. Many transmissions have gone to clutch to clutch (rather than over running clutch designs like ours) shifting which mandates electronic control. Saturn, Honda and Chrysler suffered major cutomer satisfaction issues for years until the technology caught up. They are now acceptable but not great. Then many are going to automated manuals that are computer operated. At best they are so so and still need more development. The new Ford Focus in particular is facing major cutomer lashback. Others are somewhat more acceptable but not up to American driver expectations. Consider yourself lucky that we have the gold standard in the GMC's and take care of it.

[Rob Mueller]

Greg,

Send it to Manny Trovao!

PERIOD END OF STORY!

Regards,
Rob M.

-----Original Message-----
From: Greg and April

All this talk about the tranny kickdown switch, has me wondering what
options there are for improving on the stock tranny - any thoughts?

Greg H.

[Adrien Genesoto]

Larry,

Am I thinking right that, unlike other inline trans (mounted behind the engine) the TH 425 operates in a reverse rotation?

And in no ($$$$) way can a inline trans be altered to take its place. The Revcon way would be the other alternative

Just a thought.

--
Adrien
75 Glenbrook
Yuba City,Ca.

[Greg and April]

Who?
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Rob Mueller" <robmu...@iinet.net.au>
To: <gmc...@temp.gmcnet.org>

Sent: Wednesday, December 21, 2011 21:43
Subject: Re: [GMCnet] Tranny options

> Greg,
>
> Send it to Manny Trovao!
>
> PERIOD END OF STORY!
>
> Regards,
> Rob M.
>

_______________________________________________

[Greg and April]

From what I have found, the TH425 is just a derivative of the THM400, and
that they have enough parts commonality that the majority of the parts from
the THM400 can either be used directly or with minor modification - the big
difference is that they rotate in opposite directions and the THM400 is for
RWD.

I'm not saying that a modern inline tranny could be modified, but it really
does makes me wonder as the 4L85-E, would fall right in the weight and power
class.
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Adrien Genesoto" <fixm...@syix.com>
To: <gmc...@temp.gmcnet.org>
Sent: Wednesday, December 21, 2011 22:22
Subject: Re: [GMCnet] Tranny options

>
>

> Larry,
>
> Am I thinking right that, unlike other inline trans (mounted behind the
> engine) the TH 425 operates in a reverse rotation?
>
> And in no ($$$$) way can a inline trans be altered to take its place. The
> Revcon way would be the other alternative
>
>
> Just a thought.
>

_______________________________________________

[gene Fisher]

The reason I "un-plug" the kick down is, for the engine..

I know of 3 engines that were blown when the coach was going down hill,
and the driver punched it, (trying to pass) and over revved the 455 when
the tranny "kicked down".

and then there are these mountain driving tips, that show the tranny uses
more resources when you pull it into S , rather than the kick-down.

http://gmcmotorhome.info/transmission.html#shift

gene

--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html

[Rob Mueller]

Greg,

Manny Trovao
11447 Clayton Road
San Jose, CA 95127
+1 (408) 937-1583
manny...@gmail.com

He is THE MAN when it comes to overhauling TH-425 transmissions.

Regards,
Rob M.

-----Original Message-----
From: gmclist...@temp.gmcnet.org [mailto:gmclist...@temp.gmcnet.org] On Behalf Of Greg and April
Sent: Thursday, 22 December 2011 7:49 PM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] Tranny options

Who?
.
Greg H.

[Rob Mueller]

Greg,

The second paragraph has been discussed ad infinitum on the GMCnet and as far as I know no one has ever installed any transmission
in a GMC other than a TH-425.

Oops, that's not quite right; JimB down at the COOP used Allison's and behind the monster Duramax diesels, using the Workhorse
chassis. If you want to build one of those I hope you've got lots of loose change. IIRC both of them were well and truly into the
six figure range to build.

Is the 4L85-E a FWD transmission?

Regards,
Rob M.

-----Original Message-----
From: Greg and April

From what I have found, the TH425 is just a derivative of the THM400, and
that they have enough parts commonality that the majority of the parts from
the THM400 can either be used directly or with minor modification - the big
difference is that they rotate in opposite directions and the THM400 is for
RWD.

I'm not saying that a modern inline tranny could be modified, but it really
does makes me wonder as the 4L85-E, would fall right in the weight and power
class.

Greg H.

[Gene Dotson]

jimk wrote on Wed, 21 December 2011 22:56

> Do not go with a shift kit on the transmission.
> Majority of the shift kits increase the line pressure, which can cause
> the torque converter to exert extra force forward the crank and wipe
> out the thrust bearing and the crank.
> Manny T. also mentioned this as well.
>
> Jim Kanomata
> Applied/GMC, Fremont,CA
> ji...@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _

Jim,

I am glad to hear this info. I bought a shift kit several years ago, but have never installed it. Procrastination works!
--
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators

[Matt Colie]

Greg and April wrote on Wed, 21 December 2011 20:19

> All this talk about the tranny kickdown switch, has me wondering what options there are for improving on the stock tranny - any thoughts?
>

> Greg H.

Greg,

You have not been here real long. If you had, you would know about Manuel Travao in San Jose CA. He is well know for building the "Manny Tranny". His work is quite restricted to the TH425 for GMC motorhomes. He will rebuild or supply needed parts. When he does the rebuild, he makes it as good as anybody can figure out how to make it. If there was a mod that was worth doing, he would do it. The biggest thing he recommends is changing to Mobil1 trans fluid. He must be kind of sure because he knows that this is about a 100+$us change (11~14qt@~10$).

If you have any transmission issues at all, call Manny first. He is another one of the GMC experts that are the reason we can keep going.

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit

[John Wright]

It is pretty much a non starter in putting any other transmission in
the GMC using the 455 or any other engine in the present engine/tranny
layout position. A past GMC net member worked for over 2 years in
trying to fit the Caddy Northstar engine transmission into the GMC
chassis. The real problem today is that most if not all modern engine/
tranny combinations are a transverse mounted. Revcon had to change to
a different drive train when GMC stopped making the TH425 tranny in
1979. They used a BB Chevy with a 4WD transfer case driving a
modified front axle assembly out of the pickup truck. Have never seen
one but it did work. Could be use in the GMC but you would lose
interior space as the space needed would push the steps further back.

As for the TH425 is is really a durable transmission and has been
thoroughly developed over the years. As long as you service it
regularly and change fluid every 2 years it will last a long time.

JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan

[Jim Kanomata]

Gene,
I knocked out 4 Cad engines thrust until an instructor at a trade
school pulled me to the corner and made me realize that it was not the
builders that were doing wrong, but the nut that put in the kit.
When the kit is installed on a old engine, they seem to work ok
without doing harm, but on a new engine, watch out.

Those that want to know the difference in parts 425 vs 400, Manny T is the guy.

--

Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Matt Colie]

powerjon wrote on Thu, 22 December 2011 09:08
> It is pretty much a non starter in putting any other transmission in the GMC using the 455 or any other engine in the present engine/tranny layout position. A past GMC net member worked for over 2 years in trying to fit the Caddy Northstar engine transmission into the GMC chassis. The real problem today is that most if not all modern engine/tranny combinations are a transverse mounted. Revcon had to change to a different drive train when GMC stopped making the TH425 tranny in 1979. They used a BB Chevy with a 4WD transfer case driving a modified front axle assembly out of the pickup truck. Have never seen one but it did work. Could be use in the GMC but you would lose interior space as the space needed would push the steps further back.

>
> As for the TH425 is is really a durable transmission and has been thoroughly developed over the years. As long as you service it regularly and change fluid every 2 years it will last a long time.
>
> JR Wright

JR and anybody else interested.
A recent search lead me to a Revcon/old motorhome forum. The discussion was what heavier duty front axles can be put in a BB Revcon with minimum modification. The Eaton 4500 is apparently marginal in this application. There also seem to be issues with the transfer case driving a front axle only at full load as a regular mode.

I think keeping what we have sounds like a good idea.

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit

[Dolph Santorine]

Ditto.

Check this out..... front drive, and all the hassles that go with it.

http://cgi.ebay.com/ebaymotors/Ford-F-250-?cmd=ViewItem&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D5072952698398748329&_trksid=p3286.m7&item=160701693762#ht_500wt_1182

Dolph

[noi]

Hummm - I wonder if that was built with parts from this company?:

http://dallassmithcorp.com/axleless/cab-chassis/

Carl P.

[r...@gmcnet.org]

Jim wrote on Wed, 21 December 2011 19:56

> Do not go with a shift kit on the transmission.
> Majority of the shift kits increase the line pressure, which can cause
> the torque converter to exert extra force forward the crank and wipe
> out the thrust bearing and the crank.
> Manny T. also mentioned this as well.

I don't disagree with you Jim The shift kit was installed in my Tranny 25 years ago when my kid brother helped me rebuild it on my garage floor. Fortunately we installed the mild version of the kit so the shifts aren't much more pronounced then stock, only the kick down up shift is too strong so the easy way to fix that is to unplug it. I agree the stock Tranny doesn't really need any help in its shifting ability.

--
Roy Keen
Minden,NV
76 X Glenbrook

[r...@gmcnet.org]

Bob de Kruyff wrote on Wed, 21 December 2011 18:57
> Gary, I think you are on the right track on that personally. I am constantly in the mountains here and although I still have the 3.07 with a heavy coach, I feel I have adequate ratio coverage and tend to shift as you describe. There are some inclines and declines where I just leave it in 1st or 2cnd and try not to shift at all. Revving the engine does not bother me a bit and if I can maintain a gear I would prefer that. The other thing I do that may not be recommended is leave it in L (1 first gear) and let the trans up shift and downshift by itself when it reaches it max shift rev limit. It's not very traumatic and on some of those mountain roads, I don't have time to be fooling with that "balky" shift lever. Unless modified, these transmissions will override the selector position to protect the engine and transmission and frankly the revs don't get that high.

This is probably the best reason not to install a shift kit.I lost an engine awhile back when I accidentally pulled it into low thinking it was super. If the shift kit wasn't there the design of the trans would not have allowed it to go into low.

--
Roy Keen
Minden,NV
76 X Glenbrook

[Gary Casey]

Bob,
I agree, and the only real problem (in my opinion, of course) is that cruising in high gear might be at an inefficient torque converter operating condition with a very low final drive ratio.  When you really need a higher final drive ratio is when you can't get moving, forward or in reverse.  All of my driving has lately been above 7,000 ft and I think my 3.42 final drive is more than adequate - but then my coach is about as light as they get.  The thing that a different final drive does is change the speeds at which the lower gears can be used.  An advantage of the 3.07 is that second gear runs out to a higher speed that can be very useful in the mountains.   I'm going by memory from 40 years ago, but here's how I remember most all THM transmissions work:  In manual second ("S") the transmission will downshift to second and stay there regardless of speed.  1-2 and 2-1 shifts will be almost at the normal speeds, but at maximum line pressure,
making the shifts jerky.  In manual first ("L") the transmission won't downshift until it wants to, which is usually at a lower speed than one might like.  Once in first it won't upshift until at a quite high speed, usually at a little higher speed than the normal WOT 1-2 in Drive.  At least that's the way I remember it.  Only THM-400's in Chevrolet's were much different than that.

One caution:  Some of the modifications (as implied by Bob) will override the 2-1 downshift point, allowing the transmission to make the shift at any speed.  So unless you know the transmission is unmodified, don't drop it into Low at 70 mph - you might get surprised.
Gary

Gary, I think you are on the right track on that personally. I am constantly in the mountains here and although I still have the 3.07 with a heavy coach, I feel I have adequate ratio coverage and tend to shift as you describe. There are some inclines and declines where I just leave it in 1st or 2cnd and try not to shift at all. Revving the engine does not bother me a bit and if I can maintain a gear I would prefer that. The other thing I do that may not be recommended is leave it in L (1 first gear) and let the trans upshift and downshift by itself when it reaches it max shift rev limit. It's not very traumatic and on some of those mountain roads, I don't have time to be fooling with that "balky" shift lever. Unless modified, these transmissions will override the selector position to protect the engine and transmission and frankly the revs don't get that high.

-- 
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Gary Casey]

I agree with Jim in that there is seldom a real advantage in the "shift kits" available.  But I've never heard of crankshaft thrust being an issue.  The pressure acting on the torque converter housing is converter supply, which is about 30 psi normally.  The pump drive sleeve is about 2 inches in diameter, creating a thrust of about 100 pounds.  Unless the modifier changes the converter supply orifice, it won't change a lot.  I'm not convinced that crankshaft thrust is an important consideration.
Gary Casey

Do not go with a shift kit on the transmission.
Majority of the shift kits increase the line pressure, which can cause
the torque converter to exert extra force forward the crank and wipe
out the thrust bearing and the crank.
Manny T. also mentioned this as well.

Jim Kanomata

[Bob de Kruyff]

""I'm not saying that a modern inline tranny could be modified, but it really
does makes me wonder as the 4L85-E, would fall right in the weight and power
class.
.

Greg H.
""

The 4l85E has it's roots in the THM400, although every single part is different. It's the same architecture. There ar many discussions on this subject from past years so it doesn'r hurt to restart it for newer members, but personnaly there really isn't anything to gain for the heart ache it would take to make something like that work. The whole Revcon progression would mean a major tear up of the front end of our coach.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Bob de Kruyff]

""I know of 3 engines that were blown when the coach was going down hill,
and the driver punched it, (trying to pass) and over revved the 455 when
the tranny "kicked down"""

Unless the transmission has been modified (which they may have been) the trans will shift no matter what the kickdown switch is commanding or what position the lever is in. It will upshift at it's normal WOT shift point no matter what. Now I suppose a tired engine may blow it's guts out at something around 4500 rpm, but that's a different cause.

[Johnny Bridges]

Well, it's the same tranny, but has anyone considered:
 Technical Specifications
* The Buick 455 V-8 displaced 455.72 cubic inches and produced 510 foot-pounds of torque at 2,800 rpm, more than any engine of the time. It generated 350 horsepower at 4,600 rpm. Its bore and stroke was 4.3125 inches by 3.9 inches, and it had a compression ratio of 10:1. The motor had hydraulic lifters and a four-barrel Rochester carburetor.
It's opversquare instead of undersquare which cuts the piston speed down some.  If memory serves, it winds quicker and better too.   Nice torque and HP ratings, certainl;y ballpark with the Olds unit.  And it ought to bolt to a THM425 without a lot of histrionics, it was fitted with a THM 400 like the Olds engine was.  Bit higher RPM, you could fit a 3:55 or 3:71 combo drive and have a nice setup.  Anyone wants to try it, there's an engine/trans combo - RWD - on Ebay starting at $300.

Read more: 455 Buick Engine Specs | eHow.com http://www.ehow.com/facts_7476138_455-buick-engine-specs.html#ixzz1hIJsob3e
 
-0-johnny
'76 23' transmode Norris - I wanna RB 440 and an A727, I can put a Carter carb on that...
'76 palm beach
 

________________________________

From: Bob de Kruyff <NEXT...@AOL.COM>
To: gmc...@temp.gmcnet.org

Sent: Thursday, December 22, 2011 2:44 PM

Subject: Re: [GMCnet] Tranny options

""I'm not saying that a modern inline tranny could be modified, but it really

[Bob de Kruyff]

"" Technical Specifications
* The Buick 455 V-8 displaced 455.72 cubic inches and produced 510 foot-pounds of torque at 2,800 rpm, more than any engine of the time. It generated 350 horsepower at 4,600 rpm. Its bore and stroke was 4.3125 inches by 3.9 inches, and it had a compression ratio of 10:1. The motor had hydraulic lifters and a four-barrel Rochester carburetor.
It's opversquare instead of undersquare which cuts the piston speed down some. If memory serves, it winds quicker and better too. Nice torque and HP ratings, certainl;y ballpark with the Olds unit. And it ought to bolt to a THM425 without a lot of histrionics, it was fitted with a THM 400 like the Olds engine was. Bit higher RPM, you could fit a 3:55 or 3:71 combo drive and have a nice setup. Anyone wants to try it, there's an engine/trans combo - RWD - on Ebay starting at $300.

""

Johny. I'm not real familiar with the Buick engine but memory tells me it didn't have the durability for this task. My old days at the Saginaw Transmission dyno cell recall that they basically weren't worth a s..t to put it mildly.

[Larry Davick]

The oiling system in our 455's (as I understand it) has a flaw at higher RPM's. The oil does not return to the pan quickly enough and can cause oil starvation and engine failure. Mr. Onan, Joe Mondello had a fix for this but the details are lost to me at the moment.

Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach

[John R. Lebetski]

I would think the Buick would hold up fine. (I'm partial as a Buick collector) I've never destroyed one, though I have lost an Olds rod bearing, though mostly due to other circumstances as sludge from the PO maint or lack of. Not sure how Buick would fit with the TH425, mostly on the side. However of the different versions of the 400/430/455 big block that started in 1967 as under chief designer Denny Manner, the spec you are quoting is the base 1970 high compression model. I don't think you want to buy premium fuel at 10/1 comp. So a practical 8.5/1 model would be derated from that number, with some increased durabilty.
--
John Lebetski
Chicago, IL
77 Eleganza II

[J A Holland]

During the '70s All 'SLES' Cars {South Carolina Law Enforcement Division}
Were Olds '88s with the '455/THM400 Setup and dual exaust ~
The only modification that they made to these pursuit vehicles was to turn
the top of the Air Filter Cover Upside Down {for more air intake} and install
a larger/deeper Transmission Pan {foe more fluid} ~
They would take the 'SLED' cars out of service at the end of 12 months ~
I would purchase one these {by sealed bid} every 6 months as they became available ~
{never had a problem with any of them}

~ Joe ~
--
/_]*[__][] *[__|] ~ * '73 TZE063V101887 ""
O----------OO--]* ~ '78 TZE168V100234 ""
" Joe & Lavelle " ""
'sweet home alebamy'

[Stick Miller]

Does the original discussion on this thread have anything to do with a "switch pitch" transmission.

Don't ask me why I'm asking :)
--
Stick (I used to be skinny) Miller
Americus, Georgia

[J A Holland]

Stick Miller wrote on Thu, 22 December 2011 16:40

> Does the original discussion on this thread have anything to do with a "switch pitch" transmission.
>
> Don't ask me why I'm asking :)

Stick ;

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We have switched the pitch of this thread ~

~ Joe ~
--
/_]*[__][] *[__|] ~ * '73 TZE063V101887 ""
O----------OO--]* ~ '78 TZE168V100234 ""
" Joe & Lavelle " ""
'sweet home alebamy'

_______________________________________________

[Stick Miller]

You've never forgiven me for trashing those deer seats. Your life is better off without them :)
--
Stick Miller
'78 Royale - she left me for another man
'76 X-Palm Beach
Americus, Georgia

[Johnny Bridges]

Well, I kinda defer to the gurus.  They steamed along fairly well in Skylarks of the day.  And being oversquare, you'd get slower piston speeds for a given RPM, which might be an advantage if you persist in exploring the top RPM limits of the engione. 

Realize, I was a Mopar fan in those days, their B and RB engines could and did happily blow the doors in on anything GM or Ford offered, in stock trim.  (See Brock Yates' chapter in "Sunday Driver" on the Great Musclecar Test).    Which is interesting, because a Pontiac PR guy, Jim Wangers, is usally credited with inventing the genre by stuffing a big block in a Tempest body. 
In re the big Buick motor, I wonder if the pan could be modified to pass the passenger driveshaft.  It's a front dsitributor and oil pump engine, unlike the Olds.  There might be some junk in the way.
 
--johnny
'76 23' transmode norris
'76 Palm Beach

________________________________
From: John R. Lebetski <gran...@aol.com>
To: gmc...@temp.gmcnet.org
Sent: Thursday, December 22, 2011 5:19 PM
Subject: Re: [GMCnet] tranny kickdown switch

[Rob Mueller]

Stick,

Yes and no. A switch pitch transmission has variable vanes in the torque convertor. When they are in the "high torque" mode it
generates a hell of a lot of heat and one needs a external cooler.

As I understand it when it was introduced in cars there was a switch on the throttle that would only allow it to kick in when the
throttle was wide (or really far) opened which usually happened when you were passing a vehicle. The net effect was more torque to
get you around the car quickly.

I have a switch pitch trans to go into The Blue Streak and Double Trouble; haven't decide when I'll put them in.

Regards,
Rob M.
 
-----Original Message-----

[Johnny Bridges]

Stick -
 
I'll send you the second Velvet Elvis I find.  The first one goes in my GMC.
 
--johnny
'76 23' Transmode norris
'76 palm beach

________________________________
From: J A Holland <acts23...@yahoo.com>
To: gmc...@temp.gmcnet.org
Sent: Thursday, December 22, 2011 6:18 PM

Subject: Re: [GMCnet] Tranny options

Stick Miller wrote on Thu, 22 December 2011 16:40

[Greg and April]

Thank you.
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Rob Mueller" <robmu...@iinet.net.au>
To: <gmc...@temp.gmcnet.org>
Sent: Thursday, December 22, 2011 6:25
Subject: Re: [GMCnet] Tranny options

> Greg,
>
> Manny Trovao
> 11447 Clayton Road
> San Jose, CA 95127
> +1 (408) 937-1583
> manny...@gmail.com
>
> He is THE MAN when it comes to overhauling TH-425 transmissions.
>
> Regards,
> Rob M.

[Stick Miller]

Robert Mueller wrote on Thu, 22 December 2011 18:40
> Stick,

>
> I have a switch pitch trans to go into The Blue Streak and Double Trouble; haven't decide when I'll put them in.

Well, the new-to-me X-Palm Beach has an operational one installed and working well, according to Mr. Henderson.

I don't know whether to laugh or cry.

--
Stick Miller
'78 Royale - she left me for another man
'76 X-Palm Beach

[James Hupy]

Well Stick, your first go round, I kinda laid off picking on you because
you were a novice GMCer, and I figured that you could use all the real help
that you could get. But, you went and demonstrated your affliction for all
to see by getting another after you had made a clean getaway from the first
one. Expect to suffer long and loud at the hands of this group. In reading
some of your responses here, I figure that you are up to the task at
defending yourself. Welcome back to the land of OZ.
Jim Hupy
Salem, OR
78 GMC Royale 403

[Rob Mueller]

Stick,

Laugh, it's a good thing!

Regards,
Rob

-----Original Message-----
From: Stick Miller

Well, the new-to-me X-Palm Beach has an operational one installed and working well, according to Mr. Henderson.

I don't know whether to laugh or cry.

Stick

[Bob de Kruyff]

""Is the 4L85-E a FWD transmission?""

Rob the code is:

4 4 speed
L longitudinal
85 center to center distance of gearset
E Electronic

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Rob Mueller]

Bob,

Thanks!

When no one replied to the question if it was a FWD trans I Googled it and found it's not a FWD transmission.

Regards,
Rob M.
 
-----Original Message-----

From: Bob de Kruyff

""Is the 4L85-E a FWD transmission?""

Rob the code is:

4 4 speed
L longitudinal
85 center to center distance of gearset
E Electronic

Bob

[Greg and April]

No, the 4L85-E a RWD, but it still doesn't stop me from wondering about what
might be possable, when I think about how related the TH425 and the THM400
is.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Rob Mueller" <robmu...@iinet.net.au>
To: <gmc...@temp.gmcnet.org>
Sent: Thursday, December 22, 2011 6:38
Subject: Re: [GMCnet] Tranny options

>

> Is the 4L85-E a FWD transmission?
>

> Regards,
> Rob M.

[Greg and April]

What is a shift kit and what does it do?
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Gene Dotson" <sha...@charter.net>
To: <gmc...@temp.gmcnet.org>
Sent: Thursday, December 22, 2011 7:03
Subject: Re: [GMCnet] Tranny options

>
> Jim,
>
> I am glad to hear this info. I bought a shift kit several years ago, but
> have never installed it. Procrastination works!
> --
> Gene Dotson
> 74 Canyonlands
> www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators

[Greg and April]

2 years doesn't appear to be very long - especially if less than 2K miles
are put on it.
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "John Wright" <powe...@chartermi.net>
To: <gmc...@temp.gmcnet.org>
Sent: Thursday, December 22, 2011 7:08
Subject: Re: [GMCnet] Tranny options

>
> As for the TH425 is is really a durable transmission and has been
> thoroughly developed over the years. As long as you service it
> regularly and change fluid every 2 years it will last a long time.
>
> JR Wright
> GMC Great Laker MHC
> GMC Eastern States
> GMCMHI
> 78 Buskirk 30' Stretch
> 1975 Avion (Under Reconstruction)
> Michigan

[Jim Kanomata]

Shift kits vary , but from what I have used they allow one to control
the up shifting as the lever position dictate the gear.
When down shifting, it will drop down to which gear you select. I have
accidentally downshifted and ruined the engine.
The kit will tend to give you crisper shifts as the pressure is higher
and I believe the clutch pack is compressed more.
Manny T would be able to better explain.

[John Wright]

I ran a Transgo Shift Kit in our transmission when it was rebuilt in
1999. It was an original 403 from the factory. It provided positive
shifts and manual downshifting as needed. NEVER has any problems or
issues with the transmission or the shift kit. Manual shifted down
only when using the tach to observe RPM and never saw engine go over
3600. I also had one of Jim K early 3.55 finals install by Buskirk
in 1999 the same time as the transmission was rebuilt. My shift
points under hard acceleration were about 33 mph in 1st, 53 mph in
super. When climbing a sharp grade I could hold 50+ all the way up
the hill in super. As per Jim and others I would Not install a shift
kit in a rebuild engine because of the thrust bearing failures that
have occurred in the past.

JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan

[Greg and April]

I have been following this thread, and while I have a very rough idea what
the kickdown switch is, due to the contrary nature of some of the debate
about it, I really do not fully understand its use - Could someone please
fill in the gaps, about it, what it's supposed to do and proper use of it?
.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

_______________________________________________

[Bob de Kruyff]

""I have been following this thread, and while I have a very rough idea what
the kickdown switch is, due to the contrary nature of some of the debate
about it, I really do not fully understand its use - Could someone please
fill in the gaps, about it, what it's supposed to do and proper use of it?
""

Both the THM 400 and 425 use a switch which interacts with the throttle pedal shaft(in our case) to indicate when you have floored the throttle. It actuates a solenoid in the transmission which then will allows a downshift to the next lower gear if some other parameters are also met. Its main purpose is to give a downshift for passing manuevers as well as to prevent excessive lugging if you are asking for more power (such as climbing). Lugging an engine can be much worse than letting it rev. It's a good system and allows almost instant downshifts when you need it. Granted, you can manually downshift but if you are passing, fooling with the shift lever is not always handy. The other inputs the trans gets are governor and vacuum modulator inputs. Other transmissions such as the THM 350 used a cable to do the same thing. The THM200 used the cable for the entire transmission "programming" not just downshifts and had no vacuum modulator--that proved to be a disaster. As some have
mentioned, manually selecting 2 is not quite the same as just letting the kickdown switch downshift and may be a bit better for climbing. Overall the kickdown switch should be able to handle all of your driving needs with no manual intervention. It has been successfully used on millions of applications. Sometimes the more you know the more you can worry about things that require no worries.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Greg and April]

I have a very simple philosophy.......

Stupidity is the act of making a choice that is ultimately, not in the best
interest of the person, making the choice - it can also be not in the best
interest of others ( i.e. choosing to drive while intoxicated ).

To make a good choice requires knowledge ( i.e. use the kickdown switch or
disconnect it ), it is therefore stupid to choose to remain ignorant.

If I have any choice in the matter, I choose not to be ignorant - ignorance
may be bliss, but making a bad choice is not.

I spend more time worrying about the things I don't know, because the things
that I do understand, do not scare me.

.

Greg H.

"Your health is bound to be affected if, day after day, you say the opposite
of what you feel, if you grovel before what you dislike... Our nervous
system isn't just fiction, it's part of our physical body, and it can't be
forever violated with impunity."

Doctor Zhivago

----- Original Message -----
From: "Bob de Kruyff" <NEXT...@AOL.COM>
To: <gmc...@temp.gmcnet.org>

Sent: Friday, December 23, 2011 10:50
Subject: Re: [GMCnet] tranny kickdown switch

>

[Bob de Kruyff]

""I have a very simple philosophy.......

Stupidity is the act of making a choice that is ultimately, not in the best
interest of the person, making the choice - it can also be not in the best
interest of others ( i.e. choosing to drive while intoxicated ).

To make a good choice requires knowledge ( i.e. use the kickdown switch or
disconnect it ), it is therefore stupid to choose to remain ignorant.

If I have any choice in the matter, I choose not to be ignorant - ignorance
may be bliss, but making a bad choice is not.

I spend more time worrying about the things I don't know, because the things
that I do understand, do not scare me.""

Although this net has many virtues, it also creates anxieties in some people who normally wouldn't even worry about stuff and just enjoy their units.

[Larry Davick]

Bob, it's true, but one of my favorite quotes, from one of my heroes is this: “In any moment of decision, the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing”

I never get it right, but paraphrase it as "The BEST decision you can make AT THE TIME is the RIGHT decision."

Teddy Roosevelt gets the credit for that. He certainly would have loved a GMC Motorhome to take him to all of our National Parks.

Larry Davick
Fremont, California
The Mystery Machine
'76 (ish) Palm Beach

----- Original Message -----
From: "Bob de Kruyff" <@.>
To: gmc...@temp.gmcnet.org
Sent: Friday, December 23, 2011 12:20:50 PM
Subject: Re: [GMCnet] tranny kickdown switch

[Bob de Kruyff]

""Bob, it's true, but one of my favorite quotes, from one of my heroes is this: "In any moment of decision, the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing"

I never get it right, but paraphrase it as "The BEST decision you can make AT THE TIME is the RIGHT decision."

""

My feeling is that you pick your battles. Many things on these coaches are very well engineered. Some could use attention--those are the ones I'm interested in or I would never get the coach out of the drieveway if you know what I mean. Years ago I met a women who travelled the states with her GMC. Her refigerator out of an old cabin was bungy corded to the wall. She had never heard about the net , but you know what--she was enjoying every minute of her coach and kick down switches were not on her list :)