Transmission wont move under load ie tires are on the ground but when I jack up the rear end with the tires off the ground the transmission turns the wheels just fine through all gears what could be causing this?

 

Have you checked the fluid? If the OD OFF light is flashing, read out the OBD2 codes with a scanner that can read Ford transmission codes.

 

fluid is good, no codes I just had the tc and clutch packs replaced filter is good pump is circulating fluid cooler is clear of debris I was told the transmission is in excellent shape other then the clutches needing replaced

 

When you try to move it does the engine stay at idle speed or does it rev up?

 

it revs up but only to stall speeds its like it wants to move but doeant have enough power to move