I have a Friend with an 89 Pathfinder XEV6 4wd with the 4 Speed Auto.
Yes, it has a shift control module (computer). And a I guess there is a mod out there for it so it shifts better.
All 87-95 Pathfinders AND D21 Pickups have a problem with correct shift points and they seem to rev high between gear changes.
It seems to not shift at the right times.
My friends transmission crapped out, and the AT light came on just before it never moved the rig again.
It was rebuilt, but not done right.
The Nissan Automatic has a real problem with heat, and I recommend using a good aftermarket Transcooler.
The shift servos, and the main shaft bearings can fry with too much slippage, which really is caused by the crappy shift control module, in addition to insuffcient cooling.
Its worse in 4wd, due to the increased workload.
They used the same Trans in the Subaru SVX (can you believe it?) and it has the same heat issues even being lighter. (it was a modified factory Nissan Transmission).
But, since the Engine in the SVX makes 230 HP, you can imagine the extra heat regardless of it being 500 Lbs lighter than the Pathfinder.
I heard there was some kind of service bulletin for it. Might call a good Transmission Shop.
Im sure they can help you.
I hope you dont have a bad trans, but when they are running ratty, they slip and scream alot between gears. Makes the engine sound like its racing all the time even under lower driving speeds. Its pretty annoying.