GMC Tow/Haul mode

sierra_leone

I recently purchased a new Sierra 1500 Z71 with
the trailering package. It has the Tow/Haul mode
switch on the end of the shift lever. I will be
towing a 20' Bayliner.

I currently pull my boat with a Jimmy and do not
use overdrive. If I use the Tow/Haul mode when
towing with the Sierra, can I use overdrive or
should I continue to use drive?

cdean

You should not use overdrive. It probably has a sticker on the door or in the owners manual to not tow in OD.

Put the truck in 3rd, and press the Tow/Haul button. What the Tow/Haul mode does is sharpen the shifts, and extends the shift pattern. So when you are accelerating from a stop, it will hold each gear a little longer. When it does shift, the shift will not be as 'smooth' as normal driving mode. This gives you max engine power and best transmission performance.

Besides, if you tried O/D and Tow/Haul, the computer would actually keep it in 3rd gear unless you were going down hill.

k0hb

The tow/haul feature changes the shift patterns to make better use of engine torque while towing. It DOES NOT lock out the 4th gear, or lock it in, meaning you can still get the "hunting for gears" while towing up hills, etc. Your truck has the LM7 which engine comes with the 4L60E tranny which is a light truck tranny. If you have the Z82 HD towing package, you also got a transmission cooler in that deal. Third gear works best for towing the *real* heavy loads, say more than 4,000 pounds, but your Bayliner is nowhere near that weight.

f150rules

GM trucks can't tow in OD? HMMM. Fords can tow in OD all day long. If it isn't hunting, what harm is done? I have never had a Ford transmisson failure and I always tow in OD except under extreme loads going up long steep grades, in which the GM trucks have a hard time equaling the Fords. I frequently tow heavier than rated tow capacity of my F150 and only on the grades do I ever take OD off. I have never had a transmission failure on any of my trucks either. I guess that is the torque advantage Fords have over GM.

GM recommends not towing in OD?? That's a good one.

TOW/Haul Mode only delays the shifts and firms them up. GM trucks still hunt in an out of OD with it selected. Not of much use if you have a strong transmission. Guess that says something about GM transmissions.

mgdvhman

does not just delay the shift like Ford...it re-programs the tranny for a whole different pattern..

I have Towed heavy and light...all in OD...with tow haul selected...if you are on flat/normal land...it will go into OD...it does not lock ut 4th...if you feel any hunting of gears...(should only be on hills)...put it in 3rd.

The new tow switch is a very nice option as it re-programs instead of delays..

Take it from me....I own one unlike F150....(he is always in envy of us)

...(and in severe denial)

- Tim

mgdvhman

there could be some performance diff. between my 2500 and your 1500?...

- Tim

wight1

Like Tim says, you can tow a load with a GM truck in overdrive. Unlike what f150 says, ford has NO torque advantage over GM.

GM says in the owner's manual you can tow in OD. The difference between the GM and Ford transmission is that GM was smart enough to program their PCM such that it will downshift to 3rd sooner than Ford to prevent overheating/damage to the tranny, whereas Ford will just let you pull in OD even if you are in marginal lugging conditions.

I'll put my GM 4L80 tranny up against the Ford E4OD or any other Ford unit any time. Despite what he says, if f150 is towing more than his truck's rated capacity, and goes down to 3rd gear only when going up long, steep hills, he'll be in the tranny repair shop.

mgdvhman

..you can't always feel the "lugging"....but it's doing damage...

- Tim

mgdvhman

...with GM's new tow haul....click it on and it'll do the rest...while In the normal D posistion...

- Tim

wight1

Take a look at the article in Trailer Life magazine about 2 months back on maintenance of automatic transmissions. They had a section in the article on known "weak links" in auto trannies from the Big 3.

The GM 4L80 had 2 weaknesses, one of which was related to an engine problem, not the tranny itself. The Ford E4OD tranny had about 10 listed weaknesses. And the Ford tranny is better? yeah, right!

mgdvhman

..Ford is the best!!!

- Tim

cdean

I stand corrected. The old C/Ks said not to tow in OD.

Apparently they improved the oil flow in the Silverados...which was the whole reason behind needing to pull in 3rd to begin with.

More proof to just make F150idiot spew insults and trash....

rrichf1

I thought that the whole purpose of side rear view mirrors was to prevent lugging the engine. When y'all are towing don't you keep an eye on the color of the exhaust? Clear is good and black/blue is bad.
Rich

cdean

Actually Rich, today's gas engines are practically smokeless in all conditions, thanks to the constant computer monitoring and adjusting.

mgdvhman

booooo...I liked it better when the posts from Fidiot didn't show up..

ehehehehee

- Tim

gmsucks

GM = same 30 year technology, placed in a different block with a little extra power squeezed out (at least on paper), and marketed as an all new Vortec engine.

Nothing new. Same old stuff that falls apart as the "old" old stuff. Couldn't come up with any innovative designs fast enough to outdo Ford so the new shakerado was put together last minute, using any old design they have had for 30 years. Even the body looks about the same.

GM Engineers are either not very creative or just plain lazy.

obyone

but then if you think about it, without dbhull, the Ford sales might start to pick up....LOL

meredith

After 30 or more days of inactivity....

this topic is being "frozen." It will be archived or deleted in the next 10 days or so.

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