when taking off, the tranny just slips and the tach will top out, but no movement. I can put it in reverse and it works O.K. Just happened out of the blue. I also replaced the fuel filter, but I don't think that the spilled diesel would cause the tranny to slip.No dash lights or warning lights have gone off. I have 150,000 miles, 7.3 liter. any clues? Wondereing ifI have to replace the whole thing or if able to fix. please help....

 

SOUNDS LIKE TRANS NEEDS TO BE LOOKED AT POSSIBLE CLUTCH SLIPPAGE OR VALVE BODY

 

Generally the 4R100 will blow out OD and Reverse first....since reverse is engaging I would guess your linkage is okay. I'm no expert but Im guessing your trans is burned. Could be something lesser but I wouldn't bet on it.