F-350 Transmission Question

Question

I know nothing about transmissions.  My 2007 F-350 transmission has worked fine, except during four trips across New Mexico to Albuquerque from Texas.  When towing a 12,000 pound fifth wheel at 65 mph up a rather gradual slope at approximately 7000 feet a few miles east of Clines Corners, the transmission seems to want to shift (up or down, I don’t know which) for about 20-30 seconds.  It or the engine makes a noise like it or the engine is at high rpm.  Is there a transmission sensor that is affected by atmospheric pressure?  During 35,000 miles of towing across the U.S., including the Smoky Mountains and other eastern mountains, I have not noticed this occurrence at any other time except for one brief episode at 10 mph on flat land, not towing, at 5000 feet in Albuquerque.  Does anyone have an idea of what is going on?  Can I expect a problem if I take it across the Rockies in Colorado?  Thanks in advance for your help.

bb_tx · Answer

What you are hearing may be the engine cooling fan kicking in. My '07 F350 would do that quite often during hot weather pulling the 5er fairly hard the first time I towed across the panhandle of TX. Would kick in and make a high pitched noise, almost screaming, that sounded something like the engine was reving high. Never did it not towing.

Took it to the dealer to have them check it out. They said it was the fan and did something to it and, while it still did it on occasion pulling during really hot weather, it did it much less frequently after that. Mine was still new and what ever they did they did under warranty.

road_runners · Answer

I agree with above. what you are hearing is the cooling fan kicking on. The next time you hear that noise check the engine RPM.  If it is the engine transmission you will see an increase in engine RPM, but I am sure that you will notice no RPM increase. That fan makes a lot of noise.

rv_missouri · Answer

Thanks to both of you.  However, I do not think it is the cooling fan.  For example, the one time it occurred at 5000 feet on flat land in Albuquerque, the engine had been running five minutes after having sat all night.  When the situation occurs, I can feel the transmission trying to shift.  It is not a lurching sensation, but a smooth, consistent tug.

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F-350 Transmission Question

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