Subject: 1992 mitsubishi diamante automatic transmission problem
Question:

What causes the tranny to nutral up, I have to put it in park then rev the gas before it will move in drive, some time when I go over a grade the tranny just nutrals then I have to put it in park and give it a hard rev before it will select and move in drive

Answer: Ockero,
Your fluid level may be very low, or the it may very dirty and clogged filter. For that, you'll want a fluid flush and filter changed. Else, your transmission and/or torque converter may be excessively worn and needs to be rebuilt or replaced.
Good luck!