Transmission slips when Hot

I have a 2001 Isuzu trooper with about 68,000.
The transmission shifts fine until the vehichle heats up to operating tempature. It slips completely out of gear and will not move.
I don't get it. I am hoping it is just low on fluid and not that the trans has crapped out on me.

Anyone else experience this problem and had it fixed?

Thanks in advanced from a new guy.

You're not going to like this, but especially if it has been low on trans fluid, you're out of luck. My 99 did the same thing, would slip when hot, but at 100K. Had to have the trans rebuilt to the tune of over $2000 because a retainer ring had also broken and caused gear damage. First thing I'd do is have the fluid level checked asap. 99 has no dipstick so you have to raise the car, keep it level, and remove a bolt on the side of the pan to see if it is full. Not sure about the 2001. Moderator can you help? Good luck.

The 2001 is the same way. It has no dipstick. If the tranny is bad I will just rebuild it myself. Or at least try. I can't afford $2000.