This afternoon i was stopped at a red light. I accelerate lightly and instead of the tranny shifting at like 2250ish nice and smooth, it won't shift. So i keep givin the motor a little gas and it revs all the way up to 3500 and then BAM shifts into second like i got hit by a car. It wasn't pulling the car along from like 2500-3500, just increasing revs. Same thing with the 2-3 shift. Beore this started happening it shifted firm and awesome.

The tranny was just rebuilt with a shift kit and corvette servo, also a new 2300 stall torque converter. This is no older than 2000 miles.

 

its not your trans,its the cable linkage.turn the car off then open the hood with your hand open the thottle all the way,there will be a little botton you press in to set the cable that runs to your throttle to your trans,if you cant get working right ill send you a picture to fix the problem

 

As chad89ta said you need to adjust the TV cable.
The cable is most likely adjusted too tight causing it to shift too late.

 

also if you set it to loose it will cause the trans to slide into gear,you dont what this to happen cause then you can do damage to the trans,but dont sweet it its an easy fix,and i beat you anything this is the problem