Tow/Haul Mode

HendyPhoto · October 7, 2002

Is it bad to drive in the tow/haul mode when you arent towing? I go up and down hills all the time, and I like to have the lower gear when going down hill. Would it be better to just manually shift into 3rd or 2nd? I have the allison tranny.

Thanks! (sorry for the stupid questions!!)

bluenote · October 7, 2002

Certainly you could drive solo while using tow/haul, shouldn't hurt anything....except your mileage. You'll prolly lose a mile or two per gallon on shorter drives. On a long highway trip, it shouldn't make much of a difference, I would think.

Shaners · October 7, 2002

Isn't one of the features of the Allison Tranny a grade lock feature so that it will downshift going down hill to maintain the speed? I think it can be forced to do this by tapping the brake... Some of you Ally guys chirp in here if I'm wrong.

The manual says it is not a problem to run tow/haul when empty. However it also states that it may cause unpleasant shifting and engine noise along with reduced fuel economy.

HendyPhoto · October 7, 2002

Cool! Thanks for the info, I wont worry about the tranny any more! I want to have a bumper sticker made thats says "Real men dont worry about fuel economy!" But they do worry about theyre transmission rebuild bill! Thanks again!

Jon

ausdoug · October 8, 2002

Allison has a lot of FAQ on it website about it's tranny including questions and answers on Tow/Haul mode.

cdhd2001 · October 8, 2002

Here is something you do not want to do for very long with your allison tranny,

idle in drive in traffic,

the tranny has a tendancy to suck the sump dry (oil pan) and then overheat from lack of fluid.

Found this out from a guy in the service department. Allisons are good for highway and towing, lousy for town (traffic) driving!

HendyPhoto · October 8, 2002

cdh, would it help if you shifted it to neutral while at a stop in traffic?

seatec · October 8, 2002

i just put it in park whenever i have to stop for a longer than usual light. hope thats not a problem

c10ls01 · June 6, 2007

That "feature" drives up the line pressure and changes the shift points. Hypothetically, a harsher shift means less wear on clutches, bands and stuff.

terrytucker1001 · June 7, 2007

I have a 2002 HD and the owners manual say you are to only use the tow /Haul mode when towing 3/4 of the gross vehicle weight or more, anything less can cause transmission failure.

Billdog350 · June 7, 2007

I have a 2002 HD and the owners manual say you are to only use the tow /Haul mode when towing 3/4 of the gross vehicle weight or more, anything less can cause transmission failure.

I can't comment on the Allison but I have been tuning my 4L80E in my 2003 sierra and the only thing "tow haul" does according to my transmission tables is to increase shift firmness (line pressure), decrease shift time (quicker shifts) and alter how long it will stay in a set gear based on throttle position.

I have since altered to increase my redline shifting while towing, removed some of the TM (Torque management) and reduced some of the shift times further for faster shifts. It REALLY wakes the truck up when you use tow haul mode empty now! Before it was hardly noticable.

I honestly don't see how you would reduce your trans life in Tow haul mode besides possibly the quicker shifts causing premature wear.

David Lanier · June 7, 2007

I have never heard not to use Tow-Haul unless pulling, but I'll tell you this. I have been in a position to see lots of GM (GMC/Chevy) trucks worked on, I have seen 2 Allison Trannys in over 7 years been replaced. They are just plain bullet proof. Change your spin-on filter by 50K and you'll be good. I do change mine ever 15K, but I'm being over protective.

varsis · June 7, 2007

Iv been looking into these transmissions is it worth when buying a GM to get a Allision? or is the other trannies okay? I am really looking for a worry free tranny. I had mine go in the dakota, so I am selling it asap and hoping to buy something else like gm! No more dodge for me.

David Lanier · June 7, 2007

from being in the business, I highly recommend GM Duramax and Allison tranny. I can tell you what you will have a problem with in the 2006 or older trucks, but the new trucks have not been out long enough to see any flaws. I really like the extra gear on the newer trans, mine is an 05 and I run 2400rpm at 73mph.. but the allison is the safest and the most durable trans in the 3500 market bar-none!!!!

Iv been looking into these transmissions is it worth when buying a GM to get a Allision? or is the other trannies okay? I am really looking for a worry free tranny. I had mine go in the dakota, so I am selling it asap and hoping to buy something else like gm! No more dodge for me.