Tow Haul mode

I use it on hills or if I'm towing something.

It won't hurt the engine/transmission to use the tow haul(T/H) mode all of the time. Basically it keeps the trans from shifting into overdrive. Overdrive provides better gas mileage on mostly level roads.

If you always use it you may use more fuel. Try a couple of test runs with it engaged and calculate your mileage and then try the same route and only use the T/H mode for up or down hills, compare your mileage.

Only use in in the hills.
It helps keep the speed down while descending.

I have mine on most of the time, but in Southern Ca we are going up and down hills most of the time.

I can't speak to gmc, but on Ram trucks, the T/H mode is different by year. My friend has an 04 and T/H keeps it from going into overdrive while my 05 is the opposite. I would try to find someone with the same year. JMO

I have an E450, so our tranny may be different. It also depends on the year of the vehicle. I use our T/H mode on our 2011 year primarily as a method of slowing down the vehicle. whether going down hill, or pulling off the freeway. It works like an engine brake and saves on brakes. I have not seen any value when going up hills, but if someone sees a value, please let me know.

powderman426 wrote:
I can't speak to gmc, but on Ram trucks, the T/H mode is different by year. My friend has an 04 and T/H keeps it from going into overdrive while my 05 is the opposite. I would try to find someone with the same year. JMO

Good point.
At least the same make.

Like has been said, it depends on the model of transmission you have. In my 2005 Chevy 2500HD (same transmission as the same year C motorhome with 6.0 V8), tow/haul changes the shift points for better towing performance. It does NOT keep the transmission out of overdrive but it will drop into 3rd more readily. It does nothing on downhill grades. Newer models like the 6L80E have grade braking.

rjstractor wrote:
Like has been said, it depends on the model of transmission you have. In my 2005 Chevy 2500HD (same transmission as the same year C motorhome with 6.0 V8), tow/haul changes the shift points for better towing performance. It does NOT keep the transmission out of overdrive but it will drop into 3rd more readily. It does nothing on downhill grades. Newer models like the 6L80E have grade braking.

Sounds like mine. 2004 Chevy Express 3500HD, 6.0 V8.

Use mine all the time. The E450 Drive train is hauling around a lot of weight with my particular set up. It reduces gear hunting and keeps the transmission and engine speed where it's most efficient. It also helps when descending a grade. Your manual will provide a recommendation for how it's designed to be used. Some of the smaller units would probably be fine not using it but, on the 30 footers, I am thinking that using it would be an advantage.

I use mine when towing or hauling. lol