I have an 06 Silverado 1500 LT, extra cab, 5.3, auto, 4x4, w/3:73 rears. I typically pull a loaded 5500 lb trailer w/an off-road truck loaded on it in the tow/haul mode with the cruise control set between 70 and 75. When ascending a hill in this configuration (cruise control set, tow/haul mode active), and as the truck begins to slow, the transmission will shift from overdrive into 2nd gear, completely skipping over 3rd gear. This shift occurs at about 63 mph and of course the engine is screaming at that speed in 2nd gear! The truck has 5k miles on it and the dealer tells me everything is 'normal' with this shift pattern. I traded in a truck for this one that had the exact drive train and that old truck would pull really good in both overdrive and in 3rd gear. I'm hating this new truck now. The only difference is the new truck has 20' GM factory rims and tires.The diameter of theseis the same as the 17" set-up that comes onother trucks similarly outfitted (I've checked). Help! Mike in PA

 

I have a similar issue. My truck down shifts at 75 to 2nd gear if on a hill and holds 2nd till 85. I wonder if we can program to not shift down to 2nd so early if in tow/haul mode, but shift normally in regular mode. I did not have this issue in my 93, but RPM maxed at 4500.

 

well i have read about it, and it is normal to go from O/D to 2nd, but i suggest that you just shift yourself into 3rd.

 

It is my understanding that while in tow/hual mode your transmission will not go into overdrive and the shift pattern is changed by a secondary shift table that holds the shifts longer.
I have not towed with mine yet, but I did try the feature and found that the truck did not engage o/d at all. But if I hit the button while in overdrive, nothing happend.

Bill

 

My truck difinately goes into overdrive with tow/haul on. I do not tow with it on, but I do use it with a load of firewood just to hold the shifts due to the long high bridges we have.

 

This from the 06 Silverado owners manual..........


If you have an automatic transmission, you can tow in DRIVE(D). You may want to shift the transmission to THIRD(3) or, if necessary, a lower gear selection if the transmission shifts too often, such as under heavy loads and/or hilly conditions. If you have a manual transmission and you are towing a trailer, it's better not to use the highest gear. See Tow/Haul Mode Light












And this............












How well your cruise control will work on hills depends upon your speed, load and the steepness of the hills. When going up steep hills, you may want to step on the accelerator pedal to maintain your speed. When going downhill, you may have to brake or shift to a lower gear to keep your speed down. Of course, applying the brake takes you out of cruise control. Many drivers find this to be too much trouble and do not use cruise control on steep hills.