My C4 has a mind of its own............

crushnut

New Member

Apr 27, 2003

870

0

0

Oregon

Jan 19, 2004

#1

• Jan 19, 2004

• #1

it chooses to shift at different speeds sometimes, but it doesnt do it all the time. I know it will shift different depending on how much throttle you give it, but it will shift at different speeds sometimes giving it the same amount of throttle. Any ideas as to what is up, and why it is doing this?

Thanks

 

golf4283

Active Member

May 30, 2003

1,253

1

39

Orland Park, Illinois

Jan 19, 2004

#2

• Jan 19, 2004

• #2

maybe the vacuum line is loose??? try pushing it in farther. and u can adjust the shift speeds by twisting the part where it goes in I believe so try and adjust that too. see what happens.

 

1

10secgoal

Active Member

Dec 1, 2003

2,801

3

49

San Diego

Jan 19, 2004

#3

• Jan 19, 2004

• #3

Start by testing your line that goes from you modulator to motor(should be hooked to manifold vacuun) for leaks. If it's fine pull out your modulator and get a pair of needle nose. Pull on the valve behind the modulator, make sure it moves freely. I would change to tranny fluid and modulator. Something is causing your mainline pressure to change.That's how the c-4 knows when to shift. The modulator is what controls the main line pressure. Something might be jamming the valve. See where I'm going with all this ? Trannies are the same as motors. ( A clean motor is a happy motor) Almost forgot, check to make sure motor doesn't have any vacuum leaks either. Get a guage check that first. It's the easiest.

 

G

GaPonyFarm

New Member

Jan 2, 2004

663

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0

Columbus, GA

Jan 19, 2004

#4

• Jan 19, 2004

• #4

Check your vacuum line and replace your modulator valve. The modulator valve basically sets the shift points on the C-4. Is this a recent problem? Does it shift particularly hard or soft? Any slippage? At what speeds is it shifting? When in 1st, does it feel like its in forward & reverse at the same time?

I always look to the modulator valve (its the part that the vacuum line attaches to on the tranny) for shifting point problems. Answering the other questions can help identify other possible problems. I'm assuming that you have checked the trans. fluid level and it is correct.....

 

dodgestang

Active Member

Dec 15, 2003

1,360

0

37

Cecil County, MD

Jan 19, 2004

#5

• Jan 19, 2004

• #5

crushnut said:

it chooses to shift at different speeds sometimes, but it doesnt do it all the time. I know it will shift different depending on how much throttle you give it, but it will shift at different speeds sometimes giving it the same amount of throttle. Any ideas as to what is up, and why it is doing this?

Thanks

Click to expand...

And check your fluid level at operating temp. a low or high fluid level will cause the tranny to shift 'weirdly'

 

crushnut

New Member

Apr 27, 2003

870

0

0

Oregon

Jan 20, 2004

#6

• Jan 20, 2004

• #6

Thanks guys, i fixed it. I had a vacuum leak at the manifold, damn vacuum leaks..........

 

E

EvilAirman

New Member

Apr 10, 2004

1

0

0

Apr 10, 2004

#7

• Apr 10, 2004

• #7

I am having similar problems? Also is there any links you guys can give me where i can get specs on this car, I have a 289 2v 2bbl 66 stang with a 3 speed auto. It only slips from first to second if i am going around at the right speed where the it can't decide between which gear. How could i check for a vaccum leak. But if I am giving it gas to go through the 3 gears it will never slip. For any links or specs on transmission maintainance as far as type of fluid and capacities I would be greatly appreciative.