I have a 95 5.0L F150. Not sure what the transmission type is. Anyway I noticed that when I am pulling a trailer with weight the transmission slips when I start from a stop in D. So from a stop, accelerating in D it slips into gear like letting out a clutch. If I put the truck in 1 or 2 and accelerate from a stop it does not slip at all. It also does not slip any other time. Any idea what to look for?

 

Before tossing on parts do the basics: check the transmission fluid, then do this: Fuel Injection Technical Library » How To Run a Self-Test or purchase one of these: Equus 3145 Code Reader