93 Diamante, lost overdrive/spastic shifting (automatic, ES)

My 93 Diamante has some tranny trouble. I lost overdrive, (slipping?). In OD, hitting the gas, coasting to a stop… I took it out of OD, and have been driving it for the past 3 months w/out it. The shifting is really spastic at times, especially when starting out, jerking, sifting up & down. If you let up on the gas and take it easy it settles down.

My nephew changed the tranny fluid and filter. Don’t know if this may be related…

Aside from this it drives fine:-) This is my 500.00 “midlife crisis mobile”), 186K, 2 1/2 years and all I’ve had to do is exhaust & brakes…Well except for that bad CV joint, I’ve got the part and will be putting it in this week.

Any thoughts, advice, comments? (Anybody ever replace a CV /axel on one of these?)

Thanks,

Ed