recently installed a transgo 4l60e-3 full manual kit and clutches in an 03 4l60e
reverse and 1-2-3- work great but when i click into 4th nothing seems to happen, i cant feel anything happen or see/hear rpms change at all. ideas?

 

Look at the instructions for the 3-4 shift valve if you notice they are not real clear and it seems like you install the new spring and keep the old one to and thats inccorect you disacrd the old one if you used both springs thats why you have no 4th gear.

 

could that be why there is also a flare when shifting 2-3 at WOT

 

No thats probably unrealted. Also make sure you have the servo assembled properly