tranny upshift problem - mystery

[LMedina]

Aloha Everyone, I have 2000 XLT, 53,000 miles. I'm having problems with the tranny - revs nearly to 3000 rpm before abruptly shifting into 2nd gear, and similar but not as harsh shifting from 2nd to 3rd. Been happening for a month now. I had it checked out at shop - (0) ECM codes, (0) trans codes, no pending codes. Mechanics and I inspected the tranny - everything in good condition, no debris, old fluid was a nice healthy red color - as a precaution we had the tranny flushed and linkages adjusted. It runs somewhat smoother after the tranny flush but the problem is still there. Can someone out there tell us what we missed? HELP !

 

[ExplorGM]

Tranny

Sounds similar to the problem mine is having now. Its been in the shop three times for this.Twice after being rebuilt... The overdrive pump blows a seal and on mine the OD light flashes after a while and the truck does not want to shift up.

 

[boominXplorer]

there might be crap stuck in the valve body