I have 1992 D250 intercooled with the auto tranny. It has the stock tranny cooler. Only mods are turned fuel pin 90deg and afc star wheel one turn.

When the trans is cool it get 13psi at WOT no load on flat ground. I notice that after a little normal driving the trany fluid is 180-190 measured on the hot side. Going up a grade and at WOT it will quickly rise to 220+. Once the tranny reaches its normal operating temp (180-190) boost will only be 5-6psi and will slowly reach 10psi just before it shifts.

I'm new to auto trannies and im speculating that once the tranny gets warmed up it starts slipping. Which decreases the load on the engine causing the turbo to make less boost.

I would appretiate any thoughts and comments.

 

Sounds like the TC (torque converter) is slipping which causes excess heat...i was driving on flat slope to slight hill and my tranny temps jumped up to 250ish...got a new Gorend TC and now with load cant get above 200 WOT...

 

your correct with your speculating. the torque converter is likely slipping thus creating less of a load which will result in lower boost numbers.