tractor hauler

notjustair · Dec 17, 2015

I've got an issue with my chore truck - 2000 GMC 3/4 ton. I've noticed that the Tow/Haul button on the end of the shifter does not work anymore. I hadn't given it any thought but I always try it anyway. It's been quite a while. Today I needed to use it to pull the skid steer trailer and it has no trailer brakes. The controller inside isn't registering anything. Could these two be related? Is there a fuse or anything for the tow/haul feature? I had just assumed that since it controlled the computer differently it didn't need its own separate system.

johnpop1 · Dec 17, 2015

I had a 2000 Chevy and the tow/haul quit. It was a wiring issue at the switch. My mechanic just eliminated the switch function because I never used it. Are you sure that you have good electrical connections to the trailer from the truck. With a truck that old, it may just be a connection problem at the connector interface.

glennster · Dec 17, 2015

my 06 wt has the same problem with the tow haul not working, or intermittent. the trailer brake controller is not related to the tow haul button, which controls shift points on the trans.

Jim in rush co · Dec 17, 2015

Brakes not working most likley connection at plug, I carry a can of electric cleaner in truck and have to clean connector about every other time. When my controller showes no connection, I get out cleaner then all ok.

Determined · Dec 17, 2015

If I recall when engaged the tow haul switch prevents the lock up from applying in the torque converter.
Towing in overdrive with the converter locked up it the quickest way to trash a tranny.
Going down the road in overdrive lightly tap the brake pedal and see if the RPM on the tachometer jumps up a bit, if so it is not in tow haul mode.

Doug Wilkins · Dec 17, 2015

The tow haul button does not prevent lock up of the torque converter. It helps the truck recognize that there is a load hooked behind it and adjusts timing and frequency of shift points. You are not going to ruin your transmission by running the truck without this function working. If you must tow without the towhaul and the load is heavy, drop the trans down a gear manually with the gear selector.

mj · Dec 17, 2015

(quoted from post at 13:44:57 12/17/15) The tow haul button does not prevent lock up of the torque converter. It helps the truck recognize that there is a load hooked behind it and adjusts timing and frequency of shift points. You are not going to ruin your transmission by running the truck without this function working. If you must tow without the towhaul and the load is heavy, drop the trans down a gear manually with the gear selector.

What I say also.

Determined · Dec 17, 2015

(quoted from post at 14:44:57 12/17/15) The tow haul button does not prevent lock up of the torque converter. It helps the truck recognize that there is a load hooked behind it and adjusts timing and frequency of shift points. You are not going to ruin your transmission by running the truck without this function working. If you must tow without the towhaul and the load is heavy, drop the trans down a gear manually with the gear selector.

Doug I didn't realize that was how the tow haul function was set up.
I had an 86 Chevy with a 6.2 and 700r4 it was overloaded on good days, The rest of the time thinking back to the loads I put behind that truck, it was just plain wrong.
After it ate 2 transmissions and the 3rd was going in a tranny guy told me to install a switch to inhibit lock up when I was pulling stupid loads.
Ran and abused that truck for another 15 years like that and the tranny never missed a beat.
As well as this worked for mine I assumed that was what the tow haul on the newer ones did.

Doug Wilkins · Dec 17, 2015

Its ok. That's a very common misconception that the towhaul button prevents overdrive or torque converter lockup from happening. The truck in question should have a 4l80 trans which is pretty robust and will take a fair amount of abuse. Towhaul function working or not, you got to let the truck tell you whether the load is going to prevent it from running in overdrive or not. Letting it constantly kick in and out of overdrive will create lots of heat that will eventually be the demise of the trans if done frequently.

Brian Jasper co. Ia · Dec 18, 2015

You have that exactly backwards. You most definitely want it to run in converter lock. Towing a load in overdrive that is heavy enough to prevent converter lock will very quickly overheat the trans. Tow haul mode doesn't change the engine function in anyway, it does raise shift points and line pressure along with down shifts while slowing.

tractor hauler

notjustair

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johnpop1

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glennster

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Jim in rush co

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Determined

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Doug Wilkins

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mj

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Determined

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Doug Wilkins

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Brian Jasper co. Ia

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