1999 chevy transmission

I have a 4dr 4x4 chevy tahoe with 56,200miles and the transmission shifts hard from first to second at cold and hot temps. It also takes a good fews seconds to engage when shifting it from park to drive or reverse. Anyone have any answers.
Thanks.

Bring it to trans shop. I had the same problem. The flush and fill isnt a good fix. THey need to ck the pressure sensor. $ 200, and fixed.