C-4 won't shift

Does anybody know how much vac*** is supposed to be at the modulator valve? This thing won't shift into 2nd or 3rd. Thank's!

 

Not sure what the vac*** should be but make sure the modulator pin is there.

 

I've had C4 transmissions that wouldn't shift until almost redline because of a leak in the vacuum line to the modulator. Of course, if the diaphram busted, it might give the same symptoms....

 

Straight manifold vacuum, maybe 12-15 inches.

-KK

 

Take a mitevac hand held vacuum pump remove the hose from the intake and pull a vacuum with the mitey vac and see if it holds,this test the line and the vac modulator. If it holds take a short test drive and see if it shifts,if not and the pin is in the modulator,the governor is stuck or bad

 

I'd check the line to the modulator, the modulator and if that didn't fix it the governor.

I stripped the plastic gear driving the governor on my turbo 350 and no shift and very little go.

 

Governer can somtimes stick and make them not shift make sure its at opperating temp and drive it to about 10mph and jam it in reverse sometimes unsticks the governer thats the lazy mans way better way would be to strip it down and clean the governer just make sure the mainifold port is clean and no insects have made the pipe there home.

 

My pal, CK, just went through this with his 302 SBF and C4 in his 46Ford.
He could get 2nd, but the trans would not shift into 3rd manually or automatically.

Checking vacuum it had 10" at idle as shown by my test vacuum gauge - old, but accurate.

The fools who installed the hot cam had it one tooth off.

CK got the cam in time and his cheap-o vacuum showed 12" at idle.
The car will pull 15" at a higher rpm and that's about right at this al***ude.
A touch low maybe, but it runs good and doesn't smoke.
I think it would show a little higher vacuum on my gauge, but the important part is, it's running good and shifting ok.
I know about hot cams and low vacuum at idle, but this cam ain't all that hot.

Best of all it shifts to 3rd just fine.

(The modulater was checked and the trans shop put in a 'low-vacuum' modulater, but it didn't help until the cam timing was straightened out.)

CK swapped his nice little 29 A roadste with top, fenders and good running 327 for the good looking 46 sedan.

Bad part is the 46 has been down quite a bit off and on so he can fix the ****py build done by the previous owners "builder."

I'ts getting there, once the rear parallel springs are fixed, it gets an AC which is basically why the roadster was swapped away.

I think CKs a bit sorry, the roadster was a well built car, started every time and ran great.

Now it's loaded down with bolt-on gew gaws and every time we see it at car shows it has a big stuffed animal in the front seat.
It's not CKs car any more, but it still hurts to see what happened to it....

 

Check the modulator for an adjust screw located inside the vacuum line port. If the vacuum is good and the modulator holds vacuum and there is not trans oil in the vacuum port, then you can adjust the modulator for shift firmness.

 

Thank's for the advice. I've heard about driving forward and putting it in reverse, I thought it was a joke a chevy guy would pull on a ford guy.

 

cool thread and very helpful for what im about to do, thank you!!!