D8NTransmission heating

We have a D8N 9TC02373 with a transmission heating problem. Third gear stall will heat it up then it will cool off. You can walk it 200 yards it will get in the red and take about 30 minutes to cool off.
oil cooler has been replaced with a cat reman converter has been rebuilt at local cat dealer and no change. Any help would be appreciated.

Starting from the obvious place. Radiator clean internally and externally..? fan belts, tensioners, and bearings all good..?
Also, what happens to the engine coolant temperature when the transmission heats up..? And when you say transmission heating up I assume you mean Torque Converter outlet temperature is high.

Does it take 30 minutes to "cool off" with the engine at High Idle RPM and the transmission in neutral, or is that 30 minutes with the engine shut off or idling..?

Radiator is clean belts , tensioners good and bearings, coolant stays good, It is the converter outlet temp. Does not want to cool off at high idle in neutral, very slow cool at low idle.

You will need to do some pressure testing. Cooler flow goes back to the trans as lube oil. Check the lube pressure and pump pressure.

Was the converter rebuilt because of the overheating problem? Or did problem happen after the rebuild?

I have very little dozer experience but if this was a loader or even a haul truck that would not cool off at high idle in neutral a couple things I would be looking at was flow to and from cooler and a converter housing that is flooded due to not draining correctly.

Did have a problem with a couple Allison transmissions in haul trucks acting like this years ago. Found problem with those to be a fine crack in the flange area where the two sections of the converter bolt together with 36 3/8 inch bolts. A quick look at the housing it looked fine but when running with pressure inside the converter the crack would open up and over fill the case to the point the drain back to the transmission could not keep up so converter was getting and keeping hot due to the "friction" of the oil inside the case.

Does the oil drain out of the converter housing by gravity or is there a scavenging pump? Would it be possible to run at high idle for a time then remove a drain plug some where on case to see if there is excess oil in case? Seems this was something I was told to do on a D6 that was having a problem one time.

2 pressure checks I would do.

-trans pump efficiency- trans pressure @ high idle and low idle. Difference should be no more than 10% ish
-lube pressure. All leaks upstream of the lube (last in the circuit) will be noted by lack of lube pressure.

Almost sounds like outlet relief is stuck closed. This means all displacement of pump is bypassing the cooler, either through T/C leakage or over inlet relief.

Or the inlet relief stuck open, check the setting, should be 115 at stall with cold oil. All in all sounds like not much oil flow.
Later Bob

It is obviously the cooling system! It can't possibly take 30 minutes to cool off. There is zero oil or coolant flow through the cooler. My guess is oil because just the amount of tubing/hoses in the oil system will dissipate heat faster than that.

Thanks for the info will dig deeper.

Sorry to take so long about getting back but a piece of trash got in the control valve and was causing it to stick. Thanks for the replies.