I replaced the transmission in my 94 K1500 with a GMC rebuilt tranny at 200,000 miles (about a year ago). I now have 220,000 miles and the transmission is acting funny - sometimes it will not downshift out of overdrive if you step on the gas or if the cruise control calls for more power. The rpms go way up (past redline if I let it) but it does not downshift. Of course it won't do it when I take it to ths shop -2 shops so far. Any suggestions I can give them? It is still under warranty, but I'm tired of taking it to the shop and not finding anything.