trans problem

1992 3.3 cutlass trans appears to skip or drop out of gear at speeds above 20mph. also when i slow down as i exit the freeway the vehicle acts as if it is in neutral. i then have to shift down or up and then the trans reengages. any ideas as to what the problem is? thanks the car has about 90 thousand miles.

Check the vacuum modulator on the transmission. It sounds like it is not working properly and causing the transmission not to want to shift. It is inexpensive and easy to replace. Only takes a wrench and a magnet to replace and is locate on the top of the transmission.