22FI50, 10r80 harsh downshift on highway

[Trogdor]

This afternoon on my way home from work, I was cruising down the interstate between 65-70mph and I felt and heard a sudden bang/jolt. I seriously thought someone had hit me or I had hit something. After realizing I had not, I looked at dash and notice that the truck was in 4th gear. It had slammed into 4th from 10th. After a few seconds it shifted back to 8th and on up through 10th. No more issues for the next 30 minutes.
This is the first time this has happened. In the winter I was getting some weird 3/4/5 shifts while cold but chalked that up to just being cold. Now this happened and has me a little on edge, I know that these things are finicky sometimes but dropping from 10th to 4th can't be good on it.
Truck has 33k miles on it and I do have a warranty out to 100k so I am not to worried about it, knowing that its covered but I have a long trip coming up and don't want to be stranded 2k miles from home.
Just wondering if anyone had experienced anything similar

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[ktexas04]

might not be what you want to hear but a tune (I have been using LMS for 15 years) will fix this crappy transmision strategy FORD uses on these 10 speed transmissions. Just an FYI quick fix I've found is to drive in Tow/Haul mode and for some reason the transmission doesn't act retarded in that drive mode like it does in Normal drive mode. Good luck and you aren't the only one so you will find a solution that works for you.

 

[Snakebitten]

On the 6R80 (previous generation F150 transmission) the sudden downshift from overdrive to an inappropriate low ratio (1st, in this case) was the result of a momentary failed speed sensor, and the pcm was commanding a different gear ratio to match the incorrect speed sensor data.
Ford would replace the lead frame, which hosted the speed sensor. As time went on, the failure rate increased and the NHTSA got involved. Ford redesigned the lead frame, but it was going to co$t a fortune to replace them in MILLIONS of 6R80s. So Ford was allowed to issue a recall that was to reprogram the PCM/Transmission to ignore the speed sensor data if it failed.

I don't know how similar the 10r80/6R80 designs are related to the lead frame-speed sensor, or the role the speed sensor plays in the shift strategy. But I don't think it's a leap to think that its possible that a momentary false speed report could trigger an inappropriate gear ratio selection. The 10r80 is MORE software driven than the 6R80 is, if I had to bet.

I think I remember seeing that the 10r80 has more than one "speed sensor". If so, redundancy should promise this kind of thing to be rarer?

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