I have a 94 Camry 2.2. When I am driving 45 MPH the transmissions acts like it is shifting into N or OD and then the RPMS fluctuate between idle and 1500 or so. Then when I it will shift hard because the car has decelerated. If I stay in the throttle during this it just jerks or lunges.
Have you tried replacing the fluid and filter? Have you tried to drive it with the OD deselected?
The shift solenoid(s) can fail, causing odd shifting issues.
Is this an automatic or a manual?