96 civic transmission problem

Hi all
Im hoping someone else has had this problem and lead me in the right direction.i have a 96 civc automatic What happens is the thing will go into all gears and run and shift good for
about 5 minutes then it just like its in neutral.until you turn off the car and wait for 30 -45 seconds ,restart car and it will go in gear again for a few minutes .then repeat it all over again.
I have rebuilt the a4ra trans, put in new clutches and steels and all seals ,and put in a re-manufactured torque convertor ,cleaned all the valve bodys untill the valves would drop on thier own without getting hung up ,replaced a cpc broken spring .checked all solenoids.
I have pulled it out and disassembled for a 2nd time now. What happens is the thing will go into all gears and run and shift good for about 5 minutes then it just like its in neutral.until you turn off the car and wait for 30 -45 seconds ,restart car and it will go in gear again for a few minutes .
I hooked up a gauge to the line pressure port its 125-130 and steady until the few minutes then it drops to between 20-40 lbs ,you can shut the thing off for 30-45 seconds and restart and the pressure will return to normal and go in gears again for another few minutes do you think it is a sticky valve ? ,i read the pump gears with a feeler gauge and they are within specs , thanks huge in advance.
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wrote:

Don't know too much about the details of automatic transmissions but understand the general working principles, so here goes:
The drop in line pressure would explain the "acting as if in neutral" as there would be insufficient pressure to activate the solenoids/clutches.
How do you get a drop in line pressure after 5 minutes with a reset after switch off and restart?
1) Faulty pump, sounds unlikely as it would be faulty all the time.
2) Is there a pressure relief value on the line pressure circuit, if so perhaps it is faulty, breaks open after a temperature rise.
3) Transmission fluid shortage
4) Pump not picking up fluid from the sump
Pure speculation, take it for what it's worth.
Al Moodie.
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No experience with transmissions--however, one thought. Is there a relief or pressure regulating valve in the system? If there is and it tends to hang up every so often that would account for the pressure drop. MLD
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there is a pressure regulator but it doesn't appear to be sticking ,I just don't understand how the pressure comes back up for a short time after you shut the car off for less than a minute then restart. I know aluminum cools and heats ,expands and contracts quick but I just don't see anything that would cause this,I did clean the valve ports with 600 grit sand paper as per factory service manual says is safe to do,maybe one of these valves was sticking.
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For discussion's sake--It doesn't have to be something that is sticking--just the opposite, maybe too loose (i.e. too much clearance). I had a situation where a servo valve would hang up on the first and/or second attempt of a a start (jet engine control). On the third attempt all was normal. It turned out to be "O" ring shrinkage on the piston resulting in by-pass leakage (around the piston) preventing a normal pressure build up. All it took was a modest increase in the operating fluid's temperature (resulting in a swelling/expansion of the "O" ring) to finally seal off the leakage path. I might add that this was not single unit problem but was happening to many engines and only (very significant) occurred when the ambient temperature was below 40 F. It was quite a (field) mystery for some time until some instrumented testing took place which ultimately identified the culprit. Your problem is the opposite-happening when things warmed up but still may be related to the development of a leakage path that is killing your pressure. MLD
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