trany slips wen i accelerate, why?

i got this car about 2 yrs ago and i love it. but lately whenever i take off from a start or from a low speed the engine speed (RPMs) increases but not the vechicle speed. kinda scary when gettin on the freeway. i got the vehicle from my aunt who had it sitting in frisco for 2 yrs. and i havnt changed the fluid. the fluid level is fine. other than that my 88 century is a wonderful car so if anyone knows, i would appreciate it because i want to save this car.

although the buick i have is an 84, the problem seemed to have gone away with a proper tune up. I think the mechanic said that the timeming was outta wack, i wasn't personally there to hear what he had to say. One mechanic on the other hand told me it was the cam shaft, and that is in no way related.

Your engine needs to perform well for the transmission to perform well.

Do the simple stuff first:

Do a pan service on tranny......fluid filter change, not a fluid flush. Use proper type fluid and get the fluid level as close as possible to correct.

If it doesnt help, use Lucas stop slip. Read the directions on bottle. Do not overfill.

You might want to disconnect the TCC solenoid. Maybe others can pitch in here?