Hello:

When I'm in third gear and I push the accelerator hard I can feel the tranny slip just a little, just 300 RPMs or so, is normal? because this is the first auto that I own and I'm not sure if it is.

 

You can't mean 300 RPM; that is slower than the normal idle speed.

If this is your first automatic transmission you may not know what slippage feels like. Ask a knowledgeable friend to drive your car and evaluate the transmission. Chances are you are feeling nothing more than normal torque converter operation.

Automatic transmission slippage is most noticeable during and immediately following a gear change. The engine races momentarily without a corresponding increase in vehicle speed.