Get your codes read, it might be a torque converter lockout problem, and there is a solenoid for that.

Flushing the automatic is a given at that age, you will be surprised as to how dirty the fluid is compared to what you see on the dipstick.

Check the level of the fluid when the tranny is cold, engine off. Fluid level should be at the high mark on the cold side of the dipstick. Once the tranny is warm, check the level with the engine running and in park, level should read high on the hot side.

The solenoid is a pain to remove and clean, but can be done.

Last resort is to replace the tranny.

Klaus
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Always willing to listen, just not able to take direction.