Transmission Locks wheels

[rtyndallNC]

So, I am driving my 2003 F250 pulling a 18ft trailer with a tractor on it (total weight about 9500 lbs) when I notice the tachometer go high and the tranny seems to quit pulling. Suddenly the tranny grabs in 1st and the tires lock up for a second. Before I can stop, it does it again. I managed to get off the road and stop before it does it again. I can go in reverse but not forward. I also notice the coolant temp is high but the trans temp is normal.

I check the fluid and it barely touches the bottom of the dip stick. So I get a friend to come get the trailer/tractor and I go in search of tranny fluid (the truck runs fine with no extra weight). This is when I discovered the you can't get Mercon SP or LV from your regular parts house.

So the next day I go to my local Ford dealer and tell them the story. They tell me it's a bad fuel injector. Huh?? What about the low trans fluid? I ask about a heated fluid change and he tells me the 2003 model does not have a thermal unit so it does not need a heated change and I should not do this as it could flush out "grit" that is helping the gears shift. SO I get 3 quarts if tranny fluid and pour in 2 to get the fluid to the right level and no trouble since.

What do y'all think happened? Just low fluid for the weight I was pulling? Why did the coolant temp peak but not the trans.? Does the 2003 have a internal thermostat on the tranny?

[ilike2ride]

This doesnt help but will show more than one person has same problem. If tranny fluid gets low my 05 excursion will downshift at highway speeds to 1st or 2nd gear and kills the engine. Also, after doing this it will flash tow/haul indicating a transmission problem. The big ex has 135,000, never been chipped, and no change in tranny temp. Any help appreciated!