1992 Chevy Caprice Wagon Transmission Problem

I am having an issue with my transmission. Mine will not accelerate when in reverse, at all. When I take off in overdrive, the car revs up really high until about 30mph and then finally shifts and seems to drive normal at about 45-65mph,after that the car revs really high up to about 70mph (then i slow down). No problems with gear 1 and 2. I have no clue whats going on! Any feedback would be greatly appreciated. Thank you!

Oil level? It's okay to overfill it by about a quart - try this and see if you have any changes.

Could be a plugged filter, cavitation (loose filter, although this comes with noise - a sort of whine), or a weak pump.

I won't rule out an issue with the reaction sun gear train (most likely the sun shell itself).