Duramax and towing a 10600lb 5th wheel

[Our_Place]

This is a question about the trans. Should I just leave the truck in "D" and go or should I be in manual mode and restrict it to 5th gear? The truck seems to be laboring on slight uphill grades but will pull no problem if you mash it to get it to downshift. The truck is a 2008 with the 6 speed Allison.

[larry_barnhart]

blt2ski wrote:
Bear has a Kodiak MDT d/a combo. As such, he is always in t/h mode. He has no normal mode! No different than those of us with 90's style gm pickups. The 4l80e trans does not have a t/h mode either. You have to get a 2000+ model to get this trans with a t/h option.
It is also possible depending upon gvwr of bears rig, he may not have the 1000 series. But a 2000 series if he has a dot class six 19501-26k 5500 model. The 19500 gvwr 5500 has the 1000 same as the 2500hd to 4500 models.

March

I figured your answer was the reason but I didn't know for sure. Same for the Allison 1000 installed on a MH. MH is always towing.

chevman

[blt2ski]

Bear has a Kodiak MDT d/a combo. As such, he is always in t/h mode. He has no normal mode! No different than those of us with 90's style gm pickups. The 4l80e trans does not have a t/h mode either. You have to get a 2000+ model to get this trans with a t/h option.
It is also possible depending upon gvwr of bears rig, he may not have the 1000 series. But a 2000 series if he has a dot class six 19501-26k 5500 model. The 19500 gvwr 5500 has the 1000 same as the 2500hd to 4500 models.

March

[larry_barnhart]

KD4UPL wrote:

the bear II wrote:
My Allison doesn't have a tow haul mode so I will drop it down gear by gear depending on how steep and long the grade is. I pull a 15000 lb 5th wheel and on 6% grades I'm often in second gear under 30MPH with the go pedal pushed to the floor. This seems to be a good place for the engine/trans, very smooth, no lugging and temps don't climb up.

No T/H on your Allison? How'd that happen? Did they not install that on the medium duty trucks? I've never driven one so haven't looked.

I would like to know the answer also.

chevman

[Bob_Shaw]

When I'm tow8ing, mine is always in tow/haul mode. The only time I shift it out is to get an up-shift at speeds that are below the tow/haul upshift parameters. Say a 55 mph speed limit and my up-shift happens at 62.

[sayoung]

kaydeejay wrote:
Leave it in "D" and select "Tow-Haul".
Your computer is smart enough to figure out the best gear to be in.

That's what I do.

[KD4UPL]

the bear II wrote:
My Allison doesn't have a tow haul mode so I will drop it down gear by gear depending on how steep and long the grade is. I pull a 15000 lb 5th wheel and on 6% grades I'm often in second gear under 30MPH with the go pedal pushed to the floor. This seems to be a good place for the engine/trans, very smooth, no lugging and temps don't climb up.

No T/H on your Allison? How'd that happen? Did they not install that on the medium duty trucks? I've never driven one so haven't looked.

[downtheroad]

No question...as already stated, D and Tow Haul.

This will also give you the advantage of "Grade Braking" which will take care of the "saving your brakes." deal.

[coolbreeze01]

In town and the mountains, I select the gears. The thumb shifter makes it easy, and combined with the exhaust brake, much less wear on the service brakes.

[christopherglen]

On the freeway and close to flat ground, just put it in Drive. In town, always tow/haul. Mountains, or anywhere it is hunting for a gear, tow/haul.

[Halmfamily]

Leave it in D and use the tow haul mode. I pull a 14600 lb fifth wheel with the cruise set at 62 and let the truck do what it does best, pull. The only time I turn the tow haul mode off is if I'm going down a hill and then need to shoot back up another one. In tow haul with cruise on she'll down shift to keep speed. Just let your truck work, she's a towing beast.

[the_bear_II]

My Allison doesn't have a tow haul mode so I will drop it down gear by gear depending on how steep and long the grade is. I pull a 15000 lb 5th wheel and on 6% grades I'm often in second gear under 30MPH with the go pedal pushed to the floor. This seems to be a good place for the engine/trans, very smooth, no lugging and temps don't climb up.

[Frostbitte]

kaydeejay wrote:
Leave it in "D" and select "Tow-Haul".
Your computer is smart enough to figure out the best gear to be in.

Yep, I agree too. Leave it in D.
The only time I need to shift up or down is going down or up steep grades but even then it's rare I need to fiddle with anything.

[kaydeejay]

Leave it in "D" and select "Tow-Haul".
Your computer is smart enough to figure out the best gear to be in.