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Reverse going away & coming back...

coolken84

coolken84

New member
Reverse on my recent rebuild is acting possesed. Started after about 3 weeks of driving after the rebuild. Sometimes when I put it in reverse it barely moves - I feel it go into reverse, but when I accelerate it barely moves (like the band isn't engaging) then sometimes it works fine after it's warmed up good. All the forward gears seem ok. Thoughts?
Thanks!:th_shakinghead1:
 


Is your fluid level ok? Other than possibly loose channel plate or valve body bolts there isnt a whole lot of choices. If for some reason a bunch of debris is in the fluid it could be cause some sticky valves but I would leave that as a last resort answer. You could always pop out the reverse servo and inspect the lip seal on the apply piston.
 
Well, I torqued all the valvebody & channel plate bolts to the proper specs - fluid level is right on the money, and when I installed the lip seal on the reverse servo I used a lip seal installer & petroleum jelly - it seemed to be in right...it's just strange that it works well, then works, but very poorly with slippage...don't know.
 
As for debris in the fluid, There really shouldn't be any - the rebuild was complete & the case and everything was clean. I did the flush on the transmission cooler with the trans flush, and I installed a reman torque converter.
 
Update...Now it seems as well as losing reverse when it does this, I also am starting to notice some strange behavior shifting between 1st & 2nd, kind of slipping then banging into gear. I'm pretty sure this is a pressure issue, but for the life of me don't know how it could be. I did the complete rebuild & had trannyman do the valve body work. The system has to be clean as I flushed the cooler & replaced the converter, so I don't see how I could be getting valves sticking due to debris. Would it be a good idea to take it to a trans shop that has pressure gauges to check it & also scan for codes?
 


I to have reverse problems on my 2001. consistantly when I first drive this car in the morning (hot or cold weather) my reverse works fine but as the car warms up reverse fades. I can reverse on flat surfaces if I gun the engine sometimes, uphill of any kind is not possible after warmup.
I do have the sticking preasure selenoid valve and have good and bad day's with this.(seafoam helped).

I will replace the Selenoid but wanted to get a better understanding of the Reverse problem. It seems that debri is the culprit as the harsh shifting and its debri was the start of my problems.

PS. Driving in 3rd(When needed) on the bad days realy helps this out.
 
coolken84 said:
Update...Now it seems as well as losing reverse when it does this, I also am starting to notice some strange behavior shifting between 1st & 2nd, kind of slipping then banging into gear. I'm pretty sure this is a pressure issue, but for the life of me don't know how it could be. I did the complete rebuild & had trannyman do the valve body work. The system has to be clean as I flushed the cooler & replaced the converter, so I don't see how I could be getting valves sticking due to debris. Would it be a good idea to take it to a trans shop that has pressure gauges to check it & also scan for codes?
Click to expand...

Sounds like a PSI and/or solenoid prob to me as well, and yeah. If you have a shop available have them put a Tech II on it or something and see if it points you in some direction to what it may be.
 
Well, I switched out the fluid & filter this weekend, and I found a few black rubbery chunks in the pan (maybe pieces of a seal?!?) - non-metallic. I ran it for about 20 miles with sea foam trans tune in it just before the fluid change. Forward gears seem to be okay, but last night going up an entrance ramp, while accelerating going from 2nd to 3rd it slipped badly, like the apply band just let go, jumped to like 4000rpm. I plan to take it to a shop with gauges, but anyone have thoughts before I go? P.S. Reverse still bad.
 
Wow sorry to hear all of this! The rubber pieces you find may have been chunks from the reverse piston seal. It is possible to put the seal on the piston but not sitting correctly and it may work for a while until the seal rolls over itself and gets torn up. Most trans adaptives are just asking for trouble and they will soften up all rubber parts to restore sealing abilities but the rubber can swell too much and fall apart as it becomes very weak once softened. It is not sounding good and as much as you dont want to it sounds like you may need to tear back into it to see what is going on. Also IF the rubber pieces you found are from the reverse apply piston there is a slim chance they worked back into the manual valve fluid passages in the case and are now causing other side effects but there is no way to know without looking inside.
 
Just an update - the root cause of all my troubles seems to have been an incorrect accumulator. Dave said he'd never seen one like that in a 4t65e, and now I know why...it wasn't supposed to be there! After replacing it with the correct accumulator and a transgo shift kit from David @ tripleedge , it's like a whole new transmission. Shifts are firmer, rpms are lower at high speed, and reverse is how it should be. Amazing what a difference pressure makes.
 


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