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4T65E--No Reverse!!!

L

Luminary

New member
Good morning. I'm new to this site but have been reading some of the excellent posts and information in the past that have helped me. But this one has me stumped. I recently rebuilt a 1999 Lumina for a poor young couple at my church and I'm going to give it to them. I went through the engine and the transmission and all is fine except for one minor problem--I have no reverse.

I do have all four forward gears, and since I have 1st, this is baffling me. I'd rather not pull it out, but I'm prepared for the worse. Any Ideas??
 


I believe something about a bad seal in the reverse servo can cause this. But, if I remember correctly it can be service while the tranny is in the car.

I'd have to say wait for Trannyman though. I don't have any direct experience with the issue.
 
How about if I put the piston seal in backwards? Would that disable reverse entirely? I mean there is nothing, it's just like I'm in neutral and won't change with higher engine RPM's. You would think that if it's a backwards seal or a damaged seal that you would get at least some pressure.
 
I would have to defer to trannyman as well, but I do remember reading a couple posts by him that mentioned the reverse servo and an issue with the seal. And I believe Saberwings is correct in that if that is the issue, it can be serviced/fixed in the car.

Props to you as well for doing such a good thing.
 
This is one thing that can be easily overlooked during a rebuild, but did you check to make 100% sure that the reverse servo pin is lined up properly with the reverse band? Since it is back in the car and all together then you will need to remove the intake tubing and possibly the exhaust crossover pipe to gain access to remove the reverse servo cover. This is the one on the top side of the transmission case. As the others mentioned above the lip seal on the servo piston can be of concern, but since you rebuild this then likely the seal was replaced and a new seal, as long as installed properly, will work fine. Also did you inspect the band during the rebuild to ensure that it didnt have any cracks on the lugs on the ends that engage against the anchor pin in the case and the apply pin? If the band has a crack on either end it will not apply and you will have no reverse. I would wager more on the pin being mis-aligned and that could take care of your problem.
 
Thank you all for the information. Trannyman, I disassembled the servo last night and I did indeed have the seal in backwards. Plus it had come out of the groove and the lip was a little roughed up. I put it back in (because I didn't have a new one with me) and still no reverse. It feels like it wants to engage, but nothing. My question is if I had the servo pin misaligned, wouldn't I hear some sort of noise like the drum clanging against the band on one side. I'm thinking that the pin would slam against one side of the band. No?
 


If you need a new seal I have plenty of them, I can send you one postal for the cost of shipping and just give you the seal free if you would like if that helps you out. Even if the pin or band is misalignted you likely wont hear any kind of noise. One other thing to check, make sure when the shifter is in reverse that you can push the car. Do this with the engine OFF!!! Just pull the shifter into reverse and see if the car will freely move just like it would in nuetral or drive. If it is locked like it is in park then either your shift linkage could be out of alignment OR you may have a bad park rod inside the trans that attaches to the detent plate under the shift shaft. When you pulled the servo out did you look into the hole where the servo pin goes to make sure the band was sitting in the correct position? You can take a screwdriver and push down on the band to make sure it is lined up properly.
 
Trannyman95 said:
If you need a new seal I have plenty of them, I can send you one postal for the cost of shipping and just give you the seal free if you would like if that helps you out. Even if the pin or band is misalignted you likely wont hear any kind of noise. One other thing to check, make sure when the shifter is in reverse that you can push the car. Do this with the engine OFF!!! Just pull the shifter into reverse and see if the car will freely move just like it would in nuetral or drive. If it is locked like it is in park then either your shift linkage could be out of alignment OR you may have a bad park rod inside the trans that attaches to the detent plate under the shift shaft. When you pulled the servo out did you look into the hole where the servo pin goes to make sure the band was sitting in the correct position? You can take a screwdriver and push down on the band to make sure it is lined up properly.
Click to expand...

I did not look into the hole (dumb!). It does move freely with the shifter in reverse. I have a new seal located already but thanks for your offer. You've helped immensely. I won't get to this for a couple of days but I'll report back to you on what I end up finding.
 
Trannyman,

I will take that seal off your hands. My source has informed me that they don't sell it separate. If you can tell me how to contact you, I can give you a credit card or whatever you need to expedite it.
 
Trannyman,
I just wanted to let you know that the problem was with a misaligned servo piston pin. I pulled the servo assembly apart, put on the new seal you gave me, aligned the band with a screwdriver, and I now have reverse. I gave the car away on Saturday and they were elated. It even goes in reverse now. I appreciate all your help.
 


Trannyman,

I just wanted to let you and the others know that the problem was a misaligned servo piston pin. I pulled the servo assembly apart, put the new seal in that you gave me, aligned the band with a screwdriver, and viola! we now have reverse. Thanks for all the information and direction. I gave the car away on Saturday and they were elated.
 
Great ending! That was a noble thing you did giving the car away, and some kudos to trannyman for donating the seal.
 
Hey guys, sry to bring back an old thread, but I have the exact same problem. I'm mechanically inclined but have never taken a trans apart. To get to the servo, can the trans stay in the car? Any links on disassembling a 4t65E? thanks
 


You can access it in the car but the rear exhuast manifold is over the top of it so it will need to be removed.
 
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