Have to rev to shift into drive, sometimes, help

[AmbitiousRidah]

I have been having problems with my vehicle shifting into drive. It shifts into park, reverse and neutral fine. When it is put into drive I get no response....if I rev it *sometimes* it will start pulling forward very very slowly sort of just like rolling forward then I can hear something engage or click it will still keep rolling after the engaging/clicking noise I have to keep reving it and it will eventually go into drive and it peels out cause of it engaging into drive at such high revs.....after it engages if I put it into any other gear and I come back to drive I have to repeat that. If I stay driving, *sometimes* it acts fine and shifts normally. What the heck is going on?
It is a 91 xlt....I have had the transmission filter changed along with the fluid and I was told my transmission is fine. I also replaced the brake light switch and that did not change anything. I bought a code reader and was getting 74 which is BOO failure....what else is there? Any suggestions? I had to have it towed this tuesday from a store cause it wouldnt engage into drive at all. Please reply

 

[Opera House]

How does it operate in manual 1 & 2?

One place to look is in the shift linkage. Make sure the D position lines up with the transmissions indent for D. Now for the bad news. This problem usually is associated with the forward clutch. The forward clutch engages and stays engaged any time you are in any of the forward gears. This clutch is fed fluid through seals on the center support. when these leak, the pressure drops and the clutch won't engage. This low pressure can also be caused by valve body gasket leaks and a bad pump. The low/reverse servo also engages at this time and these are known to leak severly at this age. Although not a primary cause, it could help raise pressure enough to get more time out of this transmission and is easy to replace. If it moves in manual 2, it would be a good sign that replacing this O ring would help. Try moving the shift lever next time to a slightly different position. Really sounds like it needs new seals.

If the fliud is low, check the vacuum modulator hose for fluid up on the vacuum tree on the side of the engine manifold. At this age a leaking vacuum modulator valve is a possibility. Did this problem happen before or after the fluid change. Some newer filters require different mounting hardware or else the filter drops down and sucks in air.

 

[FourXFred]

mine was doing the same thing, make sure yours is full of fluid. mine was doing that when i had a bad leak and it would run low. i would top it off and it would shift close to normal. my tranny is now in the process of being rebuilt, so id have a tranny shop check it out before it becomes a major problem.

 

[AmbitiousRidah]

I had the truck towed to AAMCO....they will start diagnosing it monday. What a pain in the .........i'll update and let you know what it turns out to be

 

[TPLYNCH]

Any word from the shop??

 

[N2MUDN91]

hes getting it totally rebuilt. everything new except the transmission housing.