So I've got an 01 suburban had the 4l60e rebuilt.had burned clutches no other problems inside the unit.git it back it the truck an notivedyhe 1st week that it would double shift into secise.you coukd actually feel it shift 2 times quickly into 2nd.well I just kept driving it cuz it's my daily and only thing I had an was happy to just have it running again.now I have noticed that is gone but it won't shift but if 1st at full throttle an I have to let off the gas just to get into 2nd an it's usually between 3k to 4500.now the wierd part is it's not slipping it just won't shift.i put in a superior 2nd gear servo.ive used the blue cat software and tuned up the shifts also to try an help...still no change.most recently I've noticed it doesn't go into lockup all the time.i just don't have any slipping so I'm not ready to give up.any ideas.sorry for such a long post guys

 

sounds like the prob could be in the valve body

 

Check Fluid Flow. A clogged filter could cause an upshift issue like that.

Should flow at least 2 Quarts in 30 seconds which is 1 gallon a minute.