1998 Ford F-150 funny shifting

My truck seem to not be shifting into 1st at all stops. It feels like I'm pulling a heavy trailer. It only does this in 1st and reverse. It seems to shift into 2nd prematurely it lugs a little in other gears. Upon down shifts the rpms are up and it down shifts and then it seems to have plenty of power. Also some times on take off I hear a churp noise, like a slipping clutch, or a hard trans engage on take off. I show no codes or check engine light. I recently installed a reman motor. I changed oil and filter, plugs, wires, air filter, soaked/cleaned the injectors, drained fuel tank, new fuel filter, new radiator, changed tranny fluid and filter. A popular transmission repairman said he thought it was a clog cat (they do seem to run hot)because of lack of power in reverse. Exhaust man doesn't think its cats. Upon his recommendation I pull two O2 sensors with no change in performance. So tranny issue, cats, or other? Thank you for your help.