When the engine is cold, in the morning, Reverse engages at idle, and I can back up.

After some spirited driving, Reverese does NOT engage at idle, but if I rev it, then it jumps into reverse.

I checked the tranny fluid this morning, and when cold it comes to exactly the "notch" on the dipstick, which I read on Brickboard was the correct position for absolutely cold fluid.

I then checked it after warming the engine,and the fluid is to the very top of the platic part of the dipstick. So maybe the transmission is OVERFILLED a little, but would that affect the reverse problem?

This is a 1993 940 Turbo, which is a new car for me, so the fluid could be ancient... although it is still red/pink. It does smell a little burnt or used, but is that possible if the color is still good?

What do y'all think? Is the tranny loaded with the wrong type of fluid from the old owner?

And is there another good alternative to Mobil One ATF? Do I need to filll with Decron 5?