Restoring - General discussions that span across many different groups of years and models > Drivetrain

Automatic Transmission Issue

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ChrisV289:
My C4 automatic transmission has been having an issue getting into reverse.  When I first start the car and let it warm up I can get into reverse just fine.  After a while though, it does not want to go.  I have to wait for it to eventually kick into reverse and even then I don't feel it really is in reverse since when i step on the gas it does not go any faster, it will, just at a snails pace.  Does the band need adjusting or is it the modulator valve causing my issue? 

ChrisV289:
Ok so an update and some questions/headache.  I put some Lucas Transmission Fix in and it seemed to go into reverse a little better but when I give it a little gas there is no a vibration and then sometimes it doesn't want to move.  Does this mean the band needs adjusting or the whole transmission should be rebuilt? 

Morsel:

--- Quote from: ChrisV289 on May 29, 2017, 10:15:28 PM ---Ok so an update and some questions/headache.  I put some Lucas Transmission Fix in and it seemed to go into reverse a little better but when I give it a little gas there is no a vibration and then sometimes it doesn't want to move.  Does this mean the band needs adjusting or the whole transmission should be rebuilt?

--- End quote ---

I don't think it would hurt to adjust the bands prior to taking the whole thing apart, it's not that hard to do if you follow the process. You can find a million post about it on the different forums. I just did it not that long ago and it was easy as long as you have a good torque wrench on hand and to follow all the torque specs as per manual. I found when backing the band adjustment screw out the proper turns, it's a good idea to use a sharpie and mark the screw on the flat side so you don't lose track of the amount of turns, plus it helps to keep it visually in that position once you are tightening the locknuts.

One thing though, once you break the seal on the outer lock nuts to adjust the bands, I would just replace them both with new ones, you'll probably get a leak if you try to use the same ones again. They are cheap and you don't want to have to redo them after you get the adjustment set.

Another thing to check, which I'm sure you probably did, is I've noticed when I first am filling my transmission with fluid, that the car doesn't shift properly until it's correctly filled. There's a process I've used that's worked great for filling the transmission that someone turned me on to that gets the car to shift properly right out of the gate. You fill with transmission fluid about 3/4 of full. Then start the car, and with the foot on the break, run through the gears slowly including park and neutral. After that, slowly add the remaining fluid until the transmission is full, obviously there's a sweet spot, and don't over fill, that's the worse thing, if anything slightly under, then take it for a cruise at slow speeds and let it shift through all the gears smoothly and naturally on it's own, don't hammer the throttle and force a kick down yet. Drive it back home and check the fluid again on a flat surface while idling in park, add fluid if necessary again making sure not to over fill. One thing is if you do over fill it and it's above the full line, you need to syphon out the extra fluid, I've had to do that and it's good to do rather than leaving it over filled. Once you've got the proper fill lever, take it for a cruise and after it shifting through everything properly and driving about another five minute, then you can hammer it and make sure the kick down shifting is working properly.

If all this fails and it's still not shifting properly, probably time for a teardown and a good look over.

Hope that helps a little,

Jason

69GT350H:
Does the transmission work in all the forward gears OK? The reverse band is usually shared with 1st gear (low).



http://www.newyorkmustangs.com/forums/how-to-service-c4-transmissions-t20090.html

ChrisV289:
Bringing this up again as the issue is still going on.  Hadn't driven the car during the summer since it is hot here but starting to cool off now.  Reverse works fine when starting it up but then once it warms up it fails to move at all.  I haven't done any adjustments yet.  The transmission I don't believe has ever been serviced at least since we have owned the car since 1992.  Mileage is around 55k we think based on condition of the car.  If I need to pull the transmission out, what is the best way?  Are the steps in the shop manual accurate or are there any suggestions.

Thanks

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