Using Tow/Haul Mode

[Screefer]

I drive a lot of steep logging roads with my Allison equipped P/U. I have gotten in the habit of using trailer tow mode (with no load or trailer)for descending these mountain roads to save brakes. Is this safe :confused: for the tranny?

The reason I ask is that my brothers 05 Dodge Cummins transmission went out and the dealer told him it was because of this same thing.

Any tips on this?

Thanks
Kim

[jbplock]

Kim,

I use Tow-Haul mode for steep hills as well ... not as often as it sounds like you are... It's designed for this ... should be OK .. sure saves the brakes ...

Here's a quote from the Allison web site ...

"Q. Automatic Grade Braking - How does it work? A. The grade-braking feature's primary purpose is to utilize engine braking to slow a heavy vehicle on steep grades in order to reduce wear on the traditional braking system. The method used to slow the vehicle is by overriding the PRNDL position, effectively pre-selecting the next lower gear range automatically. Because the transmission is electronically controlled and there is no mechanical linkage that needs to be moved for a pre-select downshift, implementation of this feature can be done completely in software with no hardware modifications.This control feature takes into consideration several factors before commanding a pre-select downshift.

These are the primary inputs to the Transmission Control Module (TCM):
-Throttle position
-(Service) Brake state
-Vehicle acceleration/deceleration
-Grade/Load

Vehicle speed These factors are continually calculated to determine when a preselect downshift is commanded."

Q. Tow/Haul vs. Normal Mode - If I use use Tow/Haul without a trailer, is that a problem? And vice versa? A. T/H can be used at any time, even when not towing. Some drivers may not like the T/H shift characteristics when the vehicle is lightly loaded, and thus normal mode would be selected. When not heavily loaded, some drivers switch from Normal to T/H mode during closed throttle downshifts from highway speeds to help slow the vehicle and then switch back to Normal mode after they've stopped. If the driver chooses not to use T/H when towing or heavily loaded, he/she can expect to see higher transmission sump temperatures, more wear and tear on the brake system, and increased shift cycling.

More info ... http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11


:)

[mark45678]

its not a dodge! they make any and every effort to place blame on the owners every time one if there trans fail..... A good friend of mine had his wifes AWD carivan trans fail with 15000 mile and again at 27000 mile, they had owned since new only 2 drivers mostly her and only towed a single snowmobile on a open trailer 900 lbs max 150 miles one way 5 time! The dealer told them they over heated the trans both times.......

You will not cause any harm to your allison using tow/haul in the hills , I have over 250000 miles on 3 trucks with duramax / allison combos and zero trans problems even with power adders.

[Screefer]

Thanks,
jbplock for the great info. I have more confidence in this truck every time I go out in it and this info makes me :D .
Mark, yeah its not a Dodge :p . I shouldn't have doubted my Chevy. I'm going to go out and wash it right now.

This really is a great web site.

[Mark Rinker]

We run all our trucks in tow/haul loaded, unloaded, uphill and downhill. I like the shift characterisitics and it definately saves on brakes.

[rob from bc canada]

I used to use tow-haul and the programmed engine-braking coming down from the ski-hill, but I found the downshifts were too aggressive, and I had to scream the engine to get it to go out of engine braking mode on the flats.

So, now I tend to control it manually by just downshifting either od lockout, or into 3rd, as needed to keep the speed down. This way I don't get nearly as much screaming engine, and still hardly use the brakes. However, this is a paved grade 6-10% where speeds are in the range of 40-50mph. On a gravel logging road, you might need tow/haul to get it to lock up at lower speeds.

Putting it in tow/haul does not automatically engage engine braking, however, I think it will cut in soner, and for the lower gears.

On mine, the engine braking will sometimes cut in at highway speeds in the REGULAR mode if I hit the brakes lightly at the start of a downgrade.