tranny problems

well I've got a 93 riviera 83000 miles on the clock and the tranny only has 1st gear and reverse, when u leave the selector in drive the rpms won't drop until you let of the gas and the car goes to neutral, but it will go in first... Can i put a tranny from a 90 riviera in the 93... Will it fit, bolt up correctly, or are they different. I thought the 88-91 vin C 3800 all had the THM440 tranny and the 92-95 had the 4T60E. i think the supercharged applications had the 4T65E-HD. Is this correct, could someone correct me if i am wrong. any help will be appreciated... thanks

The 440-T4 was re-named to the 4T60 in 1990. However, the transmission in the '90 is different from the '93 (according to GM part numbers).

I would first check and see if the transmission filter isn't plugged before you decide to change transmissions. A filter/fluid change could solve your problem. Most cars still have Reverse and sometimes 1st gear when the filter gets clogged.....

Are there any codes present? We could possibly diagnose the problem if there are codes....

The CEL is not on but i don't have a scanner for OBD1 cars, checked the fluid, it's a little overfull and it is real dirty looking, i guess the first thing to do would be a fluid and filter change and see what happens... I read somewhere also that the 93 has a common issue with bad grounds to the tranny solenoids and that would cause a loss of gears 2, 3, and 4... Any ideas?