Just recently traded my 02 screw for a a 2001 crew F-250 4x4 7.3 PSD truck has the 4R100 tranny, to pull my 8000# toy hauler truck has 135000 miles on it(i dont know the service history). Anyway, pulled my trailer a couple of times now and boy does it pull like a dream, but the other day while pulling on hwy slight uphill grade, the truck down shifted and it revved up and made whirring sound like it was slipping or something. I let off the pedal rpms came down and re applied pedal, tranny picked up and pulled like normal. On the way back from the race it did it a couple more times. I can hear the whirring sound slightly now without load, but truck seems to be fine. Anyway i'm wondering what you guys think it is. I will be towing this trailer about every other weekend now till the end of year and i down want to be left on the side of the road. Any help would be greatly appreciated

 

Before you get overly concerned do the most basic check you can: Check the tranny fluid. If it's low, high, or the fluid is brownish/black, do a trans flush and/or pan drop.

If I had to guess I'd say the sound is coming from the torque converter, simply because an old automatic tractor we had did that when going down a steep hill, you'd get a whirring from the transmission.

If the fluid is questionable and you don't know the truck's service history, I'd play it safe and change it regardless(unless it's obviously recently changed- a moderate to darker red color). If you go to the trouble of dropping the pan, you might as well change the fluid in the torque converter also(if that's possible on that truck, some newer ones no longer have drain plugs on TC's). You can do this yourself with a little know-how and aren't afraid to get a little dirty. Flushes often do more damage than help, since they flush deposits and sediment loose, clogging up lines or the filter, which is why people say "flush your toilet, not your truck".

I wouldn't worry too much about it. If the transmission starts acting up(weird/hard shifting) or it tosses codes you may have a larger issue, but if it drives perfectly normal don't worry about it.

 

Well so far all the reading i have done like you said flush your toilet not your tranny i have read many times on this board. I did have the oil changed the other day before my trip and they checked the tranny fluid and was fine, so i dont think it has to do with fluid. I do plan on dropping the pan this weekend and changing everything out, though just in case. Thanks for the input it kinda put my mind at ease, i guess now i will just drive on and see what happens. As far as fluid what type should i use? a synthetic, mercon, mercon v any suggestions? when you say codes do you mean like a check engine light on the dash or is there an actual transmission light?

 

The 4R100 tranny is fine with plain old Mercon type fluid. Sometimes that is a little difficult to find, I've used Mercon Dextron III in my truck with no ill effects.

Ford supposedly says that the "modern" Mercon V is compatible with all earlier transmissions(it was designed to be a universal ATF), though some people have reported problems.

Dextron III is everywhere, it's still a common type. I'm pretty all Mercon V is synthetic to some extent, I bought an Advance Auto store-brand Mercon V and it was listed as a synthetic.

I've heard good things about Amsoil synthetic ATF, which I believe is also branded as "universal".

I'm not totally familiar with your truck, but if there is a light on the shifter(for the O/D off button) then that is also the transmission warning light. It'll start flashing if there's a problem.

If your O/D light is on the dash, then a trans problem just turns the check engine light on. "Check engine" doesn't only mean engine problems, anything that the PCM deems as a "problem" in the vehicle makes the light come on.