99 Silverado Tranny shifting problems

I recently bought a 99 silverado ext cab Z71 with the 5.3L. I've noticed that it doesn't want to shift from 2nd to 3rd gear at the right speed when it is cold. Is there any solutions for this? Plus, like eveyone else, I also have a cold start piston slap problem. YEH!

Thanks everyone.

Your trans was made to shift late when it is cold out so the engine will warm up faster. Once it warms up it shifts ok ? let us know.

My 99 with the 4.3 does the same thing whenever the air temp is under 30 degrees (shifts from 2nd to 3rd @ 35mph instead of 30 mph). Did this from day one of delivery. Needless to say I was concerned that I got a lemon.
Chevy dealer stated this was normal..... to assist in warming up the truck.
Being suspicious, I inquired at a local trans shop operated by a friend. He confirmed what the dealer stated.