[GMCnet] Power Drive

[Rob Mueller]

G'day,

I have a 3.21 FD to install in Double Trouble and am considering installing
one of these:

http://www.casprogmc.net/powerDrive.html

I vaguely remember reading that there is a down side to these unit over the
lower ratio final drive units sold by Jim K but CRS has erased that
recollection. I went through my transmission and final drive folders but
found NADA.

What's the advantages / disadvantages of Power Drive vs. lower final drive
ratios?

Also I vaguely remember that Manny took over from Caspro, did I get that
right?

Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

[Mr.erf ERFisher]

you must mean this
http://www.casprogmc.net/powerDrive.html

gene
yep is manny

--
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]

Gene,

Yep, that's the one!

Now who's got one?

Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: Mr.erf ERFisher

you must mean this
http://www.casprogmc.net/powerDrive.html

gene
yep is manny

_______________________________________________

[Rob Mueller]

Guys,

I just did a search of the Forum and found lots of info on the power drive.

DOUH!

Nothing grossly negative so I think I'll contact Manny OFF NET.

If someone has a nightmare story and doesn't want to post it send an email
to: robmueller at iinet dot net dot au.

[Rick Williams]

Rob

I had one installed when I ordered a tranny from Manny about 8k miles ago. It has made a difference in just the same way as a final drive gear change. It added a couple hundred or so rpms and the coach has a bit more power in the hills. I was considering a final drive change when the original tranny failed so I opted for the power drive. I will be curious to see how yours performs if you do make the change. I have been considering changing the final drive to a 3.21 to get a bit more. I tow a Jeep Wrangler and it is about 3500 lbs. Big hills are still a struggle with the current setup and a stock 403.
I think Dave Lenzi removed his power drive and used a 3.21 when he installed his 8.1 engine. I do not remember his reason but I think he is pleased with the current setup.

Rick

--
Rick Williams
Gladstone, Michigan
1978 Eleganza II

[Kingsley Coach]

An interesting site and I don't think I have ever seen it before...prices
clearly stated.
Now if I didn't know him from his previous Porsche connections.....

Mike in NS

--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

[Ken Henderson]

Rob,

When I had to rebuild an engine for the GMC immediately after buying it in
'98, I had a r300 "bench overhaul" done on the transmission and installed
the Caspro Power Drive. That transmission and chain drive are now in the
X-PB my son has. I put about 63,000 miles on it before replacing it with
the new front clip; he's probably put another 5,000 mile on it. The rebuilt
torque converter failed after 10,000 miles (cracked around the hub, just
like JR Slaten's recent failure), but otherwise, there's never been any
problem whatsoever with the transmission or chain drive.

That was before JimK started selling high ratio final drives. If I had to
choose between the 3.50 chain and his 3.55 today, it would be a hard choice,
but if I had the transmission out anyway, I'd probably save the $$$ and go
with the chain.

At the time I installed my chain, they were still being distributed by Chuck
Stoddard's Caspro; Manny has now bought the rights and is selling them.

By the way, have you thoroughly investigated the 3.21 installation? A
Dixielander buddy recently bought one that we plan to install soon.
Discussing it with 3.21 experts was an eye-opener: It's not necessarily a
straight-forward, no potential problems, affair. Axle bearings & seals,
input bearing condition, etc., etc, all need attention. I'm sending you
some more info off-net.

Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com

On Sun, May 30, 2010 at 5:33 PM, Rob Mueller <robmu...@iinet.net.au>wrote:

> G'day,
>
> I have a 3.21 FD to install in Double Trouble and am considering installing
> one of these:
>
> http://www.casprogmc.net/powerDrive.html
>
> I vaguely remember reading that there is a down side to these unit over the
> lower ratio final drive units sold by Jim K but CRS has erased that
> recollection. I went through my transmission and final drive folders but
> found NADA.
>
> What's the advantages / disadvantages of Power Drive vs. lower final drive
> ratios?
>
> Also I vaguely remember that Manny took over from Caspro, did I get that
> right?
>
>

[Chris Choffat]

I have both. power drive and 3.21.

I don't have a tach, but the rpm's are definitely higher. A bit too high for my taste, but I haven't really spent any serious road time in my coach, so too early to tell. I'm also used to an overdrive tranny in my truck.

I am having a bit of irritation with the 3.21. The vent hole occasionally becomes a blow hole. It is intermittent which really annoys me. I'm told 3.21's don't have this vent and it is a 3.42. Everyone who looks at the photo's say it is a 3.21. go figure. It came with a '67 eldo switch pitch.

With this combo, I can burn a patch at every intersection if I so desire. sometimes do it unintentionally.

--
-Chr$: Perpetual SmartAss
77 Ex-Kingsley 455, Power Drive, 3:21 FD U S S Kobiashi Maru: The Engineer's Motorhome
Scottsdale, AZ

Photosite: Chrisc "It has Begun"

[Billy Massey]

You might also check with Paul Lambke about his setup.

Lambke 3.69:1 Tranny Chain Drive Sprocket Kit
Paul Lambke - phlambke@aol or Dan Stuckey - stu...@brktel.on.ca

bdub

-----Original Message-----
From: Behalf Of Rob Mueller
I have a 3.21 FD to install in Double Trouble and am considering installing
one of these:

http://www.casprogmc.net/powerDrive.html

I vaguely remember reading that there is a down side to these unit over the
lower ratio final drive units sold by Jim K but CRS has erased that
recollection. I went through my transmission and final drive folders but
found NADA.

What's the advantages / disadvantages of Power Drive vs. lower final drive
ratios?

Also I vaguely remember that Manny took over from Caspro, did I get that
right?

_______________________________________________

[Rob Mueller]

Chris,

OK, here's what I think I know!

If the final drive cover has eight (8) bolts it is a 3.21 and it has
planetary gears in it.

If the final drive cover has ten (10) bolts it's a 3.07 and it has spur
gears in it.

As far as any other ratios goes I found this:

http://www.gmcmhphotos.com/photos/data/5124/overall_drive_ratios1.pdf

I thank Ken H. for putting this together!

Mr. Erf aren't you proud of me; I found this on your website WITHOUT you
having to tell me to go look there! ;-)

I think I am safe in saying any final drive gear ratios other than 2.73,
3.07 and 3.21 are after market.

I don't know but would like to know, if the lower ratio after market gears
will fit in the 3.21 final drive.

Regards,

Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----

From: Chris Choffat

I'm told 3.21's don't have this vent and it is a 3.42. Everyone who looks
at the photo's say it is a 3.21. go figure. It came with a '67 eldo switch
pitch.

[Rob Mueller]

Chris,

I missed one of your comments; according to Caspro the 3.21 and the Power
Drive results in a final drive ratio of 3.66 to 1

http://www.casprogmc.net/3.21FinalDrive.html

Jim K has a chart on his website noting that at 65 mph the rpm difference
between a stock 3.07 and 3.66 ratio is 485rpm:

http://www.appliedgmc.com/level.itml/icOid/482

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: Chris Choffat

I have both. power drive and 3.21.

I don't have a tach, but the rpm's are definitely higher. A bit too high for
my taste, but I haven't really spent any serious road time in my coach, so
too early to tell. I'm also used to an overdrive tranny in my truck.

_______________________________________________

[Dan Borlase]

Rob...
I put in Jimmy K's 370's into my 78 (403)...what a difference !!!
Yes the rpm is slightly higher, but so much less effort going up these B.C. mountains.
Dan

[Larry]

Here's some info regarding the visual differences between the 3.21 and all of the other FD's

http://www.gmcmhphotos.com/photos/showgallery.php?cat=4399

HTH
--
Larry :)
78 Royale w/500 Caddy
Menomonie, WI.

[Glenn Giere]

I've put about 13K on mine and love it. It has the same effect as changing the rear end ratio ie: allows the engine to work in a slightly higher RPM range where it produces more power. A minor drawback to the rear end change is the need to change the speedometer drive gear in order to retain accuracy. The power drive doesn't require this.

Glenn Giere

[Jim Kanomata]

There is a difference in the method of reducing the gear ratio .
Doing it by the chain method is not uncommon, but the load ending up
on the transmission becomes greater as the transmission is still
turning at the same rate as before.
While doing the work at the final gear does not put any additional
load on the transmission.
Even Wes C. agrees on that .
Bottom line is to at least get the ratio lower to help overall
performance without consuming more fuel.

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

[Bruce Hislop]

The downside of the PowerDrive from what I can see... and read somewhere... is the increased torque developed by the changing the chain drive ratio has to be handled by the transmission as well.

Whereas if you change the final drive, the torque handled by the tranny will be reduced in favour of slightly higher rpm's.

True/false??

--
Bruce Hislop,
S. Ontario Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001

[Mr.erf ERFisher]

theory only, never a problem that I know of

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

[Jim Kanomata]

Bruce,
Your expanation is very good. I can see why I was lucky to earn a
grade of C in college in technical writing when most of the class was
pulling A and B in that class.
Many people will argue that there is no problem using the chain drive
reduction method on the coaches, but people that have been working on
these for long time admit that it does stress some of the components
on the trans.

--

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

[Mike Miller]

jimk wrote on Mon, 31 May 2010 16&#58;54
> ...

> Many people will argue that there is no problem using the
> chain drive reduction method on the coaches, but people that
> have been working on these for long time admit that it does
> stress some of the components on the trans.

Not a small thing when considering the weakest link in our drivetrain is the transmission.
--
Mike Miller
`73 26' X Painted D.
`78 23' Birchaven
Hillsboro, OR

[Rob Mueller]

G'day,

I appreciate the information noting that the Power Drive puts additional
stress on the transmission.

However, I really would like to hear from anyone (or knows someone) that has
had a transmission with the Power Drive installed that failed.

Thanks,

Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

_______________________________________________

[Chris Choffat]

Now they tell me!!!! :roll:

jimk wrote on Mon, 31 May 2010 16&#58;54

--
-Chr$: Perpetual SmartAss
77 Ex-Kingsley 455, Power Drive, 3:21 FD U S S Kobiashi Maru: The Engineer's Motorhome
Scottsdale, AZ

Photosite: Chrisc "It has Begun"

[Glenn Giere]

I've had one in mine for years. Works great. Can't find any disadvantage. No need to mess with spedo error as its ratio to rear end is unchanged.
--
Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

[John Wright]

I think that I have had almost every different drive ratio setups in the GMC’s that we have owned in the last 18 years. Our first was a 77 EL II with a 403 and a stock 3.07 ratio final drive. It was cruising at 2280 RRPM as 64 MPH. It was lacking in performance at anything under 75 MPH. Above that it got up on the cam and pulled and ran well. The first change we did was go with a 3.55 final drive. Running at 64 MPH the RPM moved up to 2880 RPM and would run well and really pull when doing a pass. Our current GMC is a 30” Buskirk Stretch with a 461 Jasper Olds with MPFI, 3.21 final and a 3.50 chain drive giving a effective 3.66 final ratio. Understand that the coach weighs14,800# pulling a loaded as a trailer Honda CRV at 3800# with a total of 18600# when we travel to and from Tucson. We run 65 MPH and pull most grades without problems. The one grade that is more difficult is the grade up the mountain from White Sands to Los Cruses a very long climb. Have done both ways and they both work well.

J.R. Wright
GMC GreatLakerTech Editor
78 Buskirk 30' Stretch
75 Avion Under Reconstruction
Michigan (On Location in Tucson)

[Bruce Hislop]

As for newer vehicles, I've owned 11 pickup trucks since 2000, all Chev and GMC. The two 2005's I had were the last pickups that actually had some
getup and go, I still have one of those trucks. Its loaded for bear with a heavy-duty commercial capper and full of tools. I get whip-lash every time
I get in that truck.

I traded the other 2005 for a 2010 and all the trucks since have been lazy dogs. Sure they do about 1400rpm or less at 95km/hr. They switch in and out
of 4 cylinder mode. When you step on the gas it spends the next second or so deciding what gear its going to change to. I can visualize the little
hour-glass spinning in its control computers. Many times its feels like you are slowing rather than accelerating in that time.

When you flip the transmission into tow/haul mode, it becomes a different truck. Accelerating from stop with my utility trailer, it may wind up to
over 4,000 rpm in each gear (6 of them) before shifting. Depending on the load it may not get to the top gear and the rpms will be in the 2-3000 range
at highway speed. This is with a total load of maybe 7-8000lbs.

According to the trucks display. my 2005 gets about 13.2 litres/100km combined city/hyway. The 2016 and 2017 I have now get about 12.7litre/100km. I
don't think the new ones will get as much life as the 2005 with all the shifting they do.
--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

[Matt Colie]

RF_Burns wrote on Wed, 20 December 2017 07:19

> As for newer vehicles, I've owned 11 pickup trucks since 2000, all Chev and GMC. The two 2005's I had were the last pickups that actually had some
> getup and go, I still have one of those trucks. Its loaded for bear with a heavy-duty commercial capper and full of tools. I get whip-lash every
> time I get in that truck.
>
> I traded the other 2005 for a 2010 and all the trucks since have been lazy dogs. Sure they do about 1400rpm or less at 95km/hr. They switch in and
> out of 4 cylinder mode. When you step on the gas it spends the next second or so deciding what gear its going to change to. I can visualize the
> little hour-glass spinning in its control computers. Many times its feels like you are slowing rather than accelerating in that time.
>
> When you flip the transmission into tow/haul mode, it becomes a different truck. Accelerating from stop with my utility trailer, it may wind up
> to over 4,000 rpm in each gear (6 of them) before shifting. Depending on the load it may not get to the top gear and the rpms will be in the 2-3000
> range at highway speed. This is with a total load of maybe 7-8000lbs.
>
> According to the trucks display. my 2005 gets about 13.2 litres/100km combined city/hyway. The 2016 and 2017 I have now get about
> 12.7litre/100km. I don't think the new ones will get as much life as the 2005 with all the shifting they do.

"That is what you have to expect for a new normal." - Guess who

That manufactures know all about this. They have to program the verhicles for emissions on a programed road test and CAFE. Pickups did not used to
be included in CAFE. But, when the overreaching government found out that people were buying pickups because they were still fun to driver, they put
an end to that as quickly as they could.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit