4R55E - Strange heat related issue on new rebuild

[Workn2fish]

I have a 1996 Explorer XLT with t-h-e V6 and just over 232000 miles. t-h-e transmission finally gave up at 229000 and was rebuilt by myself with t-h-e help of a neighbor who has done many AT rebuilds.

Besides replacing all t-h-e friction disks and t-h-e failed forward clutch hard parts, we also have installed t-h-e EPC Blow off TSB fix and t-h-e Sonnax plug kit.

t-h-e transmission runs and drives great almost all t-h-e time. t-h-ere is only one exception. When t-h-e motor is run hard and t-h-en shut down for a while, t-h-e transmission seems to get heat soaked (possibly by t-h-e catalytic converter). When this happens, t-h-e tranny will engage first fine but flares really bad going into second. It will do this for about 5 minutes before it begins to act normally again. My t-h-eory here is that it takes about 5 minutes for enough airflow under t-h-e rig to cool things back down and allow normal operation. t-h-e most common time this happens is when we've been at highway speeds for a while t-h-en drop to surface streets and stop at a store for a few minutes. When we get back in t-h-e car it normally acts up. If we drive around town for a while before stopping at t-h-e store it's fine.

Any ideas what would cause a transmission to act so drastically different based on heat?

 

[Workn2fish]

Going to hook up a pressur-e gauge and monitor transmission line pressur-e when it acts strange to see if it's losing pressur-e.

 

[Workn2fish]

A new symptom. It now acts up even when cold. I suspect I either have a worn out valvebody that was beyond rebuld or I've blown the valvebody gasket. I'll be hooking up the pressure gauge in the garage this weekend and running it through the gears to get current pressures then I'll pul the pan and replace the valvebody gaskets. If that doesn't fix it, a new valvebody (complete with all electronics) is only a measily $450 (ouch).

 

[Jack Flash]

I read no mention of replacing the servo pistons. They harden with age and cause problems (like tranny failure).

Without knowing, I have to guess that your mechanic used an inch-pound torque wrench on the valve body when it was r&r'd. Also, was the heat shield re-attached on the catalytic converter side where the servos are also located ?

,
,

J...lots of info here on the forum, time consuming to read all of it.

 

[Workn2fish]

The servo pistons were way beyond usable when we rebuilt it. The rubber edges on the cups had turned to hardened plastic. They were replaced.

Yes we used an inch pound torque wrench but I'm not conviced of the accuracy. The heat shield was replaced as well.

I ran the tranny through the gears with a pressure gauge and the pressures were within spec when just rolling forward and back in the shop. I moved the rig up the road a bit and noticed the pressures fluctuate quite a bit when I think they should be pretty solid. This leads me to think the EPC is shot (it wasn't replaced due to the $200 price tag. I will be pulling the valve body and looking for a blow in the gasket. If I find problems with the gasket, I'm going to replace them and torque it back down with a different torque wrench. If I don't have any signs of a gasket failure, I'm thinking the EPC is shot or the valvebody is just worn beyond the limits. I found a rebuilt valvebody with new electronics (uses the newer / cheaper EPC) for $430 so that may be my last option.

Thanks for the ideas.