[geomustang]

Just changed the filter and fluid, drove about a mile, stopped and would not go forward, reverse is fine.
Any Ideals?
Thanks and have a Great Day,:wavey

 

[davido30093]

Recheck the fluid level. Also be sure that you did not tighten the filter bolts too tight. Did you drain the torque converter? Did you mess with the valve body bolts at all? When you say that it will not go forward, does it seem like the clutches are slipping or it just will not go into gear?

 

[geomustang]

THANKS FOR THE INFO, DAVID.
FLUID LEVEL IS FINE, FILTER NOT OVER-TIGHTENED, NO OVER ADJUSTMENTS.
JUST DROVE ABOUT A MILE AND TRANNY STARTED SLIPPING
AND STOPPED?
THANKS AGAIN
I WILL PROBABLY DROP THE PAN AGAIN AND CHECK OUT THE VALVE
BODY.

 

[geomustang]

Stuck Valves in Valve Body????

This may be the problems.:worship

 

[Red67HT]

I have exactly same problem. I changed fluid and filter and drive less than half mile just to test that all the gears were working and everything was fine. All the gears worked and there seem to be no problem.

After that I worked on brakes and power steering etc. for few days. Now I was trying to take a test drive, but the car won't go forward. Reverse is working fine. When I try to put it on D, 2 or 1 it starts to make noise and won't go forward. When I put it on 1 and waited long enough it moves forward just enough so that managed to drive it back to garage but it feels like the whole car was shaking and the transmission made a loud noise.

Could the valves be stuck on valve body and if that is the case, how can I fix it? I don't know much about automatic transmissions...

Thanks.

 

[steph11732]

when im driving i take off and my c4 will rev really high before cetching but thats not all the time.

 

[PaulS]

If you filled and checked the fluid level - the engine has to be idling and the transmission has to be in Park.
If you check the level with the engine off it will show higher than it will with the engine running.
ALWAYS check the transmission level with the engine idling in Park.

 

[farrell262]

My 79 mustang is doing the exact same thing there is no noise made and when it is revved high it will barely inch and the reverse works great ive replaced the tranny once i just about sold it today i was thinking it was a vaccum problem but when i first filled it and drove it for about 2 or 3 miles it just stopped please let me know if you found out the problem so i can finally drive this around email me at [email protected] because im not on here much please

 

[PaulS]

If the apply piston seals in the forward clutch go bad then the forward gears will not engage. There is usually warning signs;
1. first start up of the day it takes a moment (or longer) for the transmission to go into drive. Reving the engine makes it go into gear faster and once it engages there are no problems until the next day. (reving the engine will also destroy the clutches so don't do that)
2. Later it gets bad enough that it will start slipping when the rpm drops - at stops and around corners. By this time you need an overhaul. Changing fluid does not cause this but the new fluid is thinner than the old used fluid and will make the problem appear to get worse.

Check your fluid level with the engine idling in Park first because low fluid level will cause the same symptoms. Use type F fluid only unless your builder tells you otherwise.
Paul

 

[farrell262]

i have checked the level of the fluid 3 times its all the same i know its not the clutch packs cause i rebuilt the last one and didnt work then replaced the tranny with a different one i think it is a vaccum problem or a modulator problem it just doesnt go at all except for reverse

 

[PaulS]

The vacuum has nothing to do with the clutch packs engaging.
As soon as the forward pack engages the C4 is in low gear. It stays in low gear as long as the forward clutch is applied. Second gear happens when the intermediate band applies - again vacuum will let the C4 shift automatically but with the vacuum disconnected when you put it is 2nd it will shift to second - actually over-running low gear - because it stays ready to take over - that is why if you shift to second while stopped on a hill the car will not roll back as long as the engine is running. Third gear engages when the intermediate band releases and the rev/direct clutch applies - even without vacuum this will happen at somewhere near 4800 rpm.
Since your car moves in reverse we know that the direct clutch works - that leaves the forward clutch not working - it only makes the car move in the forward direction - all forward directions. The transmission has:
1. broken sealing rings on the stator support (they feed the clutches)
2. cut, missing, or broken sealing rings on the apply piston for the forward clutch.
3. bad or missing clutches in the forward drum.
4. maladjusted internal or external linkage.
5. Leaking, cracked or broken valve body
6. low fluid level or plugged filter.

It has nothing to do with the amount of vacuum that you do or do not have at the modulator.

 

[farrell262]

well in my friends mustang just to see if that was the case we unplugged the vacuum line and it didnt want to go at all and we put it back in and worked fine but why would it work just fine then without any noises or grinding feelings it would just suddenly not work i know what the vacuum does, but i know there are ports in the tranny im not sure if they are run by the valve body or vaccum itself but one hole leads to a valve that controls forward and one that controls reverse. I just think that it would be unlikely that a brand new clutch pack would be ruined then put in a whole different tranny and change the filter in it would be doing the same exact thing, thats three times. it has to be something outside the transmission or the valve body i know its not the clutch packs cause this transmission was in perfect condition and in use when it was pulled and put into my vehicle and has no leaks except possibly when i applied more throttle but not sure we did not see the leak but we saw some stains on the road in the direction i traveled before it stopped going again but it is a high traffic area. and when i check the fluid it always varies because i keep getting fluid from along the tube even if i wait a day before i check it

 

[PaulS]

There are people who disconnect the vacuum modulator when they drag race to force the transmission to shift at the highest rpm. With the modulator disconnected the 1-2 shift happens at around 40-45 mph and the 2-3 shift happens at 65 - 75 mph.
as you slow down it will automatically shift (harshly) into a lower gear as it comes into range. what you say about the transmission not working at all just can't happen by disconnecting the vacuum from the modulator.
Since you know it has to be the vacuum you obviously know more than I do - I have only been working on these transmissions for 40 years.

 

[rodbender]

Well said Paul.:bigthumbsup

 

[farrell262]

well first off i didnt say it didnt work at all eventually at higher RPMs it shifted and i failed to mention that im not asking for an arguement so sarcasm is not needed i have little money and little tools just the basics so please if you can give me a diagnosis i will run over the symptoms again. the fluid looks a little bit burnt already it will not shift at all when i get near to redlining it the car will slightly start to budge there is no grinding noises or any noises out of the ordinary and it will go into reverse easily but shifts into it hard. on my friends truck he had the same problem but it was a cable that was somewhere ontop of his EFI since mine is a 2bbl i dont think it was the same problem what i have been thinking it is, is the valve body maybe some dirt has got into it because i took the tranny out and put that one in on nothing but dirt grass and tire ramps as i am sure you have experienced as well if you have anymore info please let me know i have no experience in this except for what i have done recently i may just put in a t-5 if possible
:needabreak

 

[alexs223]

your vacuum may not be doing its job check that out and it should help