Ford C6 Transmission Problem
Steve Gerland
automatically. It will shift OK manually using the shift
lever. Forced downshift works OK, just no auto upshift when
starting from a stop. Everything else seems to be OK, no
lack of torque transfer to the wheels.
Could this be something that can be resolved without removing
the transmission from the car? Maybe something sticking in
the valve body?
Any help appreciated,
Steve
"58" is spam blocker.
John Kunkel
Whenever shift problems occur in the C6 first check the condition of the
vacuum lines to the modulator and, if necessary, replace the modulator.
Also check the fitting in the intake manifold where the vacuum hose at-
taches. The fitting will sometimes be clogged up with carbon.
John
Herman
Herman
Steve Gerland wrote:
C6 automatic transmission in a '77 Ford Ranchero will not shift
automatically. It will shift OK manually using the shift
lever. Forced downshift works OK, just no auto upshift when
starting from a stop. Everything else seems to be OK, no
lack of torque transfer to the wheels.
Could this be something that can be resolved without removing
the transmission from the car? Maybe something sticking in
the valve body?
Any help appreciated,
Steve"58" is spam blocker.
gee...@inreach.com
>
> C6 automatic transmission in a '77 Ford Ranchero will not shift
> automatically. It will shift OK manually using the shift
> lever. Forced downshift works OK, just no auto upshift when
> starting from a stop. Everything else seems to be OK, no
> lack of torque transfer to the wheels.
>
> Could this be something that can be resolved without removing
> the transmission from the car? Maybe something sticking in
> the valve body?
>
> Any help appreciated,
> Steve
Hmmm...getting some mixed signals here. You say it won't upshift, but
you say that forced downshifts are ok. How can you have a forced
downshift if it isn't in second or third D range, which would require an
upshift? This trans starts in first and stays in first in L, starts in
second and stays in second in 2, and is supposed to shift 1-2-3 in D.
What happens when you shift manually from 2 to D at high speed, low
load?
Things to check: Vacuum modulator, fittings, and tubing, as another
poster mentioned. Kickdown linkage and proper spring back at the
trans. Take off the linkage from the carb to the trans, and see what
happens. My experience with governors is that they don't malfunction
very often--the valves are very simple and rugged.
If you replace the vacuum modulator, make sure the stripe color is the
same as your old one. I've had some weird things happen with incorrect
modulators.
Is it smoking lots of blue smoke and losing trans fluid? Is the level
ok?
It can be a sticky valve somewhere. Check the simplest things first.
Let us know what happens!
Gerard
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Juneriver
bit, that is probably where the problem is at. Look for other bad sections
of line or replace the modulator. Your description of symptoms eliminates
almost everything but the vacuum and/or the modulator itself.
Jamie
Juneriver
usually, while engine oil will smoke blue.....any body know why this is????
Jamie
gee...@inreach.com wrote in message <363EB8...@inreach.com>...
Steve Gerland
transmission problem.
gee...@inreach.com wrote:
: Hmmm...getting some mixed signals here. You say it won't upshift, but
: you say that forced downshifts are ok. How can you have a forced
: downshift if it isn't in second or third D range, which would require an
: upshift? This trans starts in first and stays in first in L, starts in
: second and stays in second in 2, and is supposed to shift 1-2-3 in D.
Let me help try to clarify this a little if I can. It will upshift
manually, but not automatically. I have also found that the problem is
intermittent. It just started working one day, then quit again. If I run
it through the gears manually and get up to speed in 'D', it will kick
down like it normally should at wide open throttle.
: What happens when you shift manually from 2 to D at high speed, low
: load?
It shifts normally under this condition. The problem is predominantly
with the 1-2 shift. When it gets stuck in first, I can pull the shift
lever down manually to first, then move it back to second and the
transmission will then shift into second.
: Things to check: Vacuum modulator, fittings, and tubing, as another
: poster mentioned. Kickdown linkage and proper spring back at the
: trans. Take off the linkage from the carb to the trans, and see what
: happens. My experience with governors is that they don't malfunction
: very often--the valves are very simple and rugged.
Since last weekend I checked the vacuum lines and found a old brittle
section of hose at the modulator diaphragm and replaced the suspect
piece of hose. Things started working normally for a short period of time
afterward, but quickly deteriorated again.
Will check out the kickdown linkage next - have not done that yet. If
nothing is wrong there I will try the modulator diaphragm. One question
about that. Will trans fluid drain out when the diaphragm is removed?
: If you replace the vacuum modulator, make sure the stripe color is the
: same as your old one. I've had some weird things happen with incorrect
: modulators.
Will take note of this. Thanks for the advice.
This made me just think of something else. The transmission was rebuilt
at AAMCO about four years ago. Has run OK since, but maybe the modulator
was replaced at that time with an 'inexact' replacement. I suppose there
is no way to really know for certain.
: Is it smoking lots of blue smoke and losing trans fluid? Is the level
: ok?
No smoke, no loss of fluid.
: It can be a sticky valve somewhere. Check the simplest things first.
: Let us know what happens!
Will keep updates posted as this progresses...
: Gerard
gee...@inreach.com
> : you say that forced downshifts are ok. How can you have a forced
> : downshift if it isn't in second or third D range, which would require an
> : upshift? This trans starts in first and stays in first in L, starts in
> : second and stays in second in 2, and is supposed to shift 1-2-3 in D.
>
> Let me help try to clarify this a little if I can. It will upshift
> manually, but not automatically. I have also found that the problem is
> intermittent. It just started working one day, then quit again. If I run
> it through the gears manually and get up to speed in 'D', it will kick
> down like it normally should at wide open throttle.
Since the trans starts in first in L and D, and starts in second in 2,
you will get a shift when putting the trans from D to 2 if the trans is
in first or third.
> : What happens when you shift manually from 2 to D at high speed, low
> : load?
>
> It shifts normally under this condition. The problem is predominantly
> with the 1-2 shift. When it gets stuck in first, I can pull the shift
> lever down manually to first, then move it back to second and the
> transmission will then shift into second.
All you need to do is pull the shifter into 2.
> : Things to check: Vacuum modulator, fittings, and tubing, as another
> : poster mentioned. Kickdown linkage and proper spring back at the
> : trans. Take off the linkage from the carb to the trans, and see what
> : happens. My experience with governors is that they don't malfunction
> : very often--the valves are very simple and rugged.
>
> Since last weekend I checked the vacuum lines and found a old brittle
> section of hose at the modulator diaphragm and replaced the suspect
> piece of hose. Things started working normally for a short period of time
> afterward, but quickly deteriorated again.
Check it again, at both ends. Was there any fluid in the line when you
removed it?
> Will check out the kickdown linkage next - have not done that yet. If
> nothing is wrong there I will try the modulator diaphragm. One question
> about that. Will trans fluid drain out when the diaphragm is removed?
Yes. Have a drain pan ready. Also, if it's a screw in modulator, make
sure you have the new gasket. If a press in, make sure you have an
o-ring.
> : If you replace the vacuum modulator, make sure the stripe color is the
> : same as your old one. I've had some weird things happen with incorrect
> : modulators.
>
> Will take note of this. Thanks for the advice.
>
> This made me just think of something else. The transmission was rebuilt
> at AAMCO about four years ago. Has run OK since, but maybe the modulator
> was replaced at that time with an 'inexact' replacement. I suppose there
> is no way to really know for certain.
>
> : Is it smoking lots of blue smoke and losing trans fluid? Is the level
> : ok?
>
> No smoke, no loss of fluid.
>
> : It can be a sticky valve somewhere. Check the simplest things first.
Gerard
dbug
wrote:
>C6 automatic transmission in a '77 Ford Ranchero will not shift
>automatically. It will shift OK manually using the shift
>lever. Forced downshift works OK, just no auto upshift when
>starting from a stop. Everything else seems to be OK, no
>lack of torque transfer to the wheels.
>
>Could this be something that can be resolved without removing
>the transmission from the car? Maybe something sticking in
>the valve body?
>
>Any help appreciated,
> Steve
>
>
>
>"58" is spam blocker.
>
It sounds like your 1-2 shift is the problem. The 1-2 shift is
controll either by the vacuum modulator or the road speed governor.
The modulator takes care of normal 1-2 shifts. The road speed
governor handles the wide open throttle 1-2 shift or 2-1 downshift.
The first place I would go is make sure the vacuum lines are in good
shape with no leaks along with all the other vacuum system as the
modulator can be affected by any loss of vacuumm that reduces the
vacuum signal to it. Use a hand vacuum pump and guage to check the
modulator lines for leakage. If the lines are not leaking, replace
and adjust the modulator. There are two generic replacements - a
screw-in or clamp-in type. They are adjustable with a very small
flat blade screwdrive inserted into the vacuum connection tube of the
modulator. You raise the shift point by screwing clockwise and reduce
the shift point (speed) counterclockwise.
If this doesn't fix it, you are in for some internal adjustments or
repairs better left to a trans man that knows what he is doing.
Mark Cook
I have been racing a C-6 in circle track car since 1991. I have plugged
off the hose to modulator valve. The transmission will shift up and down
on it own, but only at certain rpms. If a restart is slow enough, the
car will start in low, and shift though the gears without me having to
move the shifter.
The point is that the transmission should shift by itself, but not at a
confortable "street" rpm.
This makes me wonder if something is wrong with the valve body or maybe
the governor is not working properly.
Have you had the valve body out?
Mark
Steve Gerland
gee...@inreach.com wrote:
: >
: > Since last weekend I checked the vacuum lines and found a old brittle
: > section of hose at the modulator diaphragm and replaced the suspect
: > piece of hose. Things started working normally for a short period of time
: > afterward, but quickly deteriorated again.
: Check it again, at both ends. Was there any fluid in the line when you
: removed it?
No fluid in the line at all. Also, this is a steel line with the
exception of the short hose pieces at each end.
: > Will check out the kickdown linkage next - have not done that yet. If
: > nothing is wrong there I will try the modulator diaphragm. One question
: > about that. Will trans fluid drain out when the diaphragm is removed?
: Yes. Have a drain pan ready. Also, if it's a screw in modulator, make
: sure you have the new gasket. If a press in, make sure you have an
: o-ring.
Checked out the kickdown linkage today. All is well and good there -
nothing binding or loose or worn. Spring is in place and has good
tension.
:
: > : If you replace the vacuum modulator, make sure the stripe color is the
: > : same as your old one. I've had some weird things happen with incorrect
: > : modulators.
Ordered a replacement modulator diaphragm from my local NAPA parts place
today. Will pick it up and replace the original one tomorrow. They asked
about the stripe color when I called, too.
: > : It can be a sticky valve somewhere. Check the simplest things first.
Went and got Haynes C6 transmission book today, just so I can attempt to
understand the internal workings better.
Steve
"58" is spam blocker
RWard76547
Also pull vacuum line off modulater and see if any fluid comes out. If it does
modulater needs repacing.
gee...@inreach.com
>
I never knew there was such a thing. Where can I buy one?
dbug
The Haynes book is pretty decent. I got one at Pep Boys for $11. The
ATSG manual has some important info that is not int the Haynes. You
can get that one through a trans parts supplier..NAPA has them as well
as others.
gee...@inreach.com
Hey, thanks! Gotta get me some new O2 sensors for my 133,000 mile 86
5.0 today, so I'll find out about the books....always need more books...
Steve Gerland
: I never knew there was such a thing. Where can I buy one?
Got it from AutoZone.
: Gerard
Steve Gerland
I replaced the vacuum modulator today, which seems to have fixed the
problem. Since it was an intermittent problem, only time will tell
if it is *really* fixed, or if today was just a good day for being
intermittent.
gee...@inreach.com
>
> gee...@inreach.com wrote:
> : > Went and got Haynes C6 transmission book today,
> : >
> : > Steve
>
> : I never knew there was such a thing. Where can I buy one?
>
> Got it from AutoZone.
I just picked up one from my local Car Quest auto parts store. It has
c3, c4,c5, c6, and aod. Lots of illustrations, so it looks like it'll
be a good addition to my others.
Thanks!