I just bought a rebuilt 700r4. I was told it was out of an 88 firebird and had only ~10k since rebuild. I installed a transgo and put the tranny in, works great on the street, no signs of slipping or anything going out. I just made my first 1/4 pass and the trans wouldn't shift into 3rd at WOT but shifts fine with 50-75% throttle. I tried all the basic stuff, correct amount of fluid and TV adjustment. Have any ideas on what would cause this? BTW, this only occurs when I manually shift.