C4 Trans issue

bigjeff53 · May 16, 2019

Hi
I am having trouble with my 77 c4 trans. Had it rebuilt by a shop worked great for a while. Every once in a while when I stop it won't engage in drive or reverse. I can shift in all the gears and nothing. If I shut it down for a bit it will work again. Any idea's?
Thanks

Viperwolf1 · May 17, 2019

What exactly do you mean by "Every once in a while when I stop"? Are you just stopping with the brakes, are you shutting the engine off, or what? Have you checked the fluid level?

Rustytruck · May 17, 2019

Sounds like low on transmission fluid. Start up the truck and shift slowly through all the shifter positions and back up to park. Leaving the truck in park with the engine running set the parking brake. Check the tranny fluid. With cold fluid you want the tranny fluid just showing on the end of the dipstick.
1/2 a quart of tranny fluid can make a big difference on how well the tranny shifts.

Codiak · May 17, 2019

Mine did the same after my rebuild. It would drive fine at first, but after it warmed up; the engine would rev like I shifted it into neutral. If I shut it off and then started it back after a few minutes it would shift ok until about 35 mph. Then it would do it again. I found the filter in the pan was getting stopped up with some kind of material. After about 3 flushes and filter cleaning; it hasn't done it since.

bigjeff53 · May 17, 2019

77 C4 issue

What I mean is for instance I drove around the other day for about 20 miles then stopped to get fuel. When I started it up shifted into drive and nothing. Went through all the gears and reverse, still nothing. Shut it off waited a bit started it again tried drive again did not work, went to park and back to drive then kicked in. Went home put it park got out to open shop door and it did it again. Fluid is full and clean. Some times it does this and some time it fine. This transmission only has maybe 150 miles on since pro rebuild

Viperwolf1 · May 17, 2019

What's the possibility of bringing it back to the pro to fix it?

Might be a loose valve body or valve plate.

Local Boy · May 17, 2019

Are you manually shifting it? Auto trans do not like that.... unless you have a manual valve body...

I'm certainly not a trans expert, but I believe 1st gear and reverse are linked together... and manually shifting it would negatively affect its engagement...

Looking forward to hear from those who are much more technically knowledgeable than me on this...

Aloha

Viperwolf1 · May 17, 2019

Local Boy said:
Are you manually shifting it? Auto trans do not like that.... unless you have a manual valve body...

I'm certainly not a trans expert, but I believe 1st gear and reverse are linked together... and manually shifting it would negatively affect its engagement...

Looking forward to hear from those who are much more technically knowledgeable than me on this...

Aloha

I believe you are right. You are not a trans expert.

Local Boy · May 17, 2019

hahahaha

Thanks for your confirmation...

My apologies to the OP for confusing the matter...

bax · May 17, 2019

I think it is going to be media in the valve body. Fine particles "trash" causing the valve body to be sticky. This can happen after a rebuild. Plus the c 4 valve body can be tricky. They don't like to be over tightened during assembly. I would drop the pan. drain it real good, even shift it thru the gears to move out whatever fluid is in the valve body. install a new filter, fill with new or filter the old fluid. then add some trans valve body lube / additive and run it around. I bet it clears up. However since it is a new rebuild, take it back to the pro and have him do this. If he had cleaned it really good before assembly he / you may not be having this problem.

Viperwolf1 · May 17, 2019

To move forward you only need the forward clutch to engage. Reverse requires the high/reverse clutch and the rear band. Both of those are controlled only by movement of the manual valve, which is connected to the shifter. That's why I think there is a loss of pressure causing the issue. Loose valve body or valve plates bleeding pressure needed to engage clutches.

Tcb3078 · May 18, 2019

I had similar issues. Pulled mine, issue was sticky governor and valves

bigjeff53 · May 25, 2019

C4 Trans issue solved

Finally got to the bottom of my trans issue. Took it to a new shop. They thought is was the valve body as with everyone else. Turned out it was a missing shim in front of the stater. The old shop forgot one. So when trans was cold the fluid would keep them tight and when hot would let pressure bypass. Had to pull trans out to fix it.

bax · May 26, 2019

Thats what I was going to say next.

. Glad you got it fixed. Sucks about all the trouble.

C4 Trans issue

bigjeff53

New Member

Viperwolf1

electron whisperer

Rustytruck

Bronco Guru

Codiak

New Member

bigjeff53

New Member

Viperwolf1

electron whisperer

Local Boy

Full Member

Viperwolf1

electron whisperer

Local Boy

Full Member

bax

Old Member

Viperwolf1

electron whisperer

Tcb3078

Sr. Member

bigjeff53

New Member

bax

Old Member

Similar threads