I have a year old rebuilt 5r55e trans in my 99 4wd. Been working fine but over the past few months it has been having a weird problem of free reving when it goes to shift to 3rd gear. It started as a cold fluid issue at first but now its happening all the time.
Today I dropped the pan and installed the Trans Go kit which made no differance at all. Still shifts very slow and soft. The EPC was replaced when the trans was rebuilt last year also.

Anyone ever have this problem?

 

Mine would slip shifting from second to third, but not from first to third. Ended up replacing it with a factory reman because we could find a problem with the valve body or shift solenoids.