Everything went in smooth, got the 4X4 low & Hi working...motor is plenty for off-roading, sand duning e.t.c
Finally got it on the freeway and that's when Problems started happening... The original HD truck came with 29" tall tires with 4.10 rear/front gears, the Ford F-100 has 32" tall tires with 3.50 gears...For some reason it won't stay in overdrive, it keeps downshifting to 3rd gear, sometimes into 2nd gear...If I manually shift thru the gears it shifts really good, but if I put it in drive and let it shift by itself, the tranny hesitates from 2nd to 3rd and to 4th. In the tune, I made changes in the speedo calculator that it has 3.50 gears and 32" tall tires but didn't fix the downshifting or hesitation...
A buddy of mine told me my problem is the Torque Converter apply and release speeds? Could it be? I have never adjusted the TCC at all....
The transmission only has 47,000 original miles

Any help or guidance will be appreciated...