I had a '97 Silverado Excab and did have a strange tranny problem. Sometimes, but not always when you would run at normal speeds for 10-15 minutes then stop at a stop sign, pulling out it would shift (more like slam) into second. Stop the truck, shut if off and start it back up and it was fine...until you did the over 35mph process for 10 minutes again. The problem was it wasn't happening consistantly making trouble shooting difficult. The truck was out of warranty so I didn't take it back to the dealer, but did find aloyt about the tranny. It's a very solid unit, but seems there are electronic servos in it that are very sensitive to below spec voltages. I've heard guys replaced valve bodies for big bucks and still couldn't isolate the shifting hard problems. I also read that a tranny shop was faced with the same hard shifting problem on a customers truck and they went round on that one many a times. Well, someone left the interior lights on in it on one of it's trips to the Tran man and they had to put in a battery to get it into the shop. Now the end result was the tranny stopped shifting hard. I read that and figured...what the heck, it's a cheap try. I put my battery on charge overnight and the thing worked fine for a month before the mysterious second shift slam came back. Put it back on overnight charge and the same results. Go figure. So I got a new battery, except it came with a new '01 2500HD Crew Cab.