I am having issues with my transmission, but only while towing. I'll be cruising along at 100 kph and the truck will downshift into 5th for no apparent reason. I tried a variety of speeds ie. 80, 90, 100, 110, and still it would downshift into 5th. I am towing an empty trailer which maybe weighs 2000 lbs with no headwind and very little to no grade on the road. I also tried in towhaul mode but that made no difference. Funny thing is, I would drive up a fairly steep incline at these same speeds and it then decides not to downshift. I also took it to the dealer and they reflashed the tranny but it still continues. Not sure what to do at this point. Any help would be appreciated.

 

5th and 6th are both OD gears so it's not a big issue if it's changing down. Mine will do the same thing when I tow my trailer but mainly because of the wind resistance of the trailer. Is you trailer open or closed type?

 

Cruise control ? That shouldn't be used when towing especially with tow mode.

 

didn't realize that. Funny they never mentioned this at the dealer. They figured something was wrong, hence the reflash they did. Would definitely save on fuel if it would remain in 6th though. Its a dump trailer so it is open. Thanks for the reply

 

Was driving without cruise control. Should have mentioned that earlier I guess

 

Mine won't hold much load in 6th. The manual says the 6spd will shift a lot more than a traditional 4spd.

 

I have a 2010 2wd 4.6 3v with 6 speed. I have 33" tires and experience the same even with no load. The truck downshifts if the wind blows. Tried various speeds, no difference.

 

Mine does the same when towing, much more so when tow/haul is on. Sometimes on a long flat road I turn off tow/haul and it will kick it up to 6 then I just pout tow/haul back on and all is well. I think the truck picks up on the slightest pedal movement and downshifts.

Fwiw, I towed 130 miles each way and tested mpg with t/h. Off was 9.8mpg and on I got 11.something.

 

FWIW, I have found that the truck downshifts much less in hilly or windy conditions if you don't use cruise control. Obviously, you are allowing small fluctuations in the speed when you do this, but to me that is much less annoying than having it downshift from 6th to 5th all of the time. By doing this you can anticipate slight hills and overpasses and speed up slightly to keep it from downshifting. When the cruise is engaged, the truck will slow down and then be forced to shift down to try and maintain a constant speed. If I had my wish, we would have a 6th gear lock-out on or trucks for towing. I've now had trucks with a 4-speed, a 5-speed and 6-speed auto trans. To me the 5-speed was perfect.

 

Your not meant to tow with cruise control on!

 

I tow with cruise control on all the time. Then again, I have a manual tranny.......