tranny problems with acceleration

I bought a 1994 lumina euro with 3.1 liter engine and completly love it. but a few weeks ago i was getting on the freeway and the engine would rev up but seem not to tranfer all the power to the wheels. it only happens when i try to accelerate too quickly and after several seconds it speeds up. i found that if i floor it to get on the freeway and when it hits 4000 rpm let off the gas and then accelerate again it shifts better. is it the tranny or is it because im being stupid about the engine type.(i used to have a 4.0 liter jeep cherokee). any feedback about this problem would be appreciated.

thanks,
Anizalb1288

Welcome to the Forums. Check simple things like trans fluid level, as low fluid can cause high rpm/heavy load slippage.