I was hauling a camper with a 1997 F350 Diesel. After an hour of driving the O/D light began to flash and the transmission began to slip as it forced fluid out the dipstick tube and breather hole. I lost maybe 1 quart while driving. The trans has gradually gotten worse with light driving, difficulty going into Reverse or Drive. The trans is 4R100 type 4speed automatic.
Any ideas on what may have malfunctioned?

It's 20 years old, hauling a camper. Time for a rebuild I would guess.

It's 20 years old, hauling a camper. Time for a rebuild I would guess.

Thanks for the suggestion. To bad Ford didn't build the trans as good as that 7.3L!

It's possible nothing serious is really wrong. The ATF may simply be boiling over, due to the summer heat and load--a common problem in Texas. If you don't have a supplemental transmission cooler, I would install one. I would also drop and clean the pan, install a new transmission filter, and refill with full synthetic ATF meeting the Mercon V specification. Full synthetic ATF has a higher coefficient of heat, allowing the transmission to run cooler, shift better, and last longer. After refilling the transmission, move the shift lever through each gear (PRNDL), pausing several seconds in each gear. Check fluid level when the transmission is at normal operating temperature and in Park.

Thanks! in fact, it was running much warmer than I expected. Ill give it a try.