I have about 1200 miles on my 89 gta since I put everything back together. New engine 383 and new 700r4 trans. Everything seems to work good except at high speed. If I easy the car up to about 90 mph everything seems good and then if I nail it to the floor it down shifts and it really hauls until it hits about 105 and tries to shift into high gear. Trans completly slips and tach goes right to rev limiter. When I let off quick and coast a second and step on the gas everything is fine. It is almost like the tranny is missing the shift. Whats up with that?