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2006 gmc envoy_slt_xl
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Discussion Starter · #1 ·
Okay first time poster so bare with me... I own a 2003 chev silverado besides my 06 envoy xl slt. I think these trucks have the same tranny and was wondering is there anyway to install a tow haul mode on the envoy or tb.. There are both computer controled so i dont think it would be to hard... May be it has been done but i have not seen it on here any info would be nice...:bonk:
 

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2005 chevy trailblazer_ls
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:tiphatWelcome to the site! Don't understand your question, but one of our resident experts will chime in shortly with the info you need!:thumbsup: I just put mine in third instead of drive to pull my trailer.
 

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2004 gmc
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The PCM could have been designed with a tow/haul mode and button, but alas it wasn't. Best one can do is choose a tune with tow modifications from a vendor like pcmforless.com, but unless you get flash software like EFILive, you can't change from one to the other quickly, much less on the fly.

Are there handheld programmers yet to do this for us I haven't been keeping up with?
 

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2009 chevy
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I'm not familiar with the feature, but it definitely is part of the PCM programming.

A good possibility, that it only keeps the tranny from shifting into overdrive.

It may be one of the reasons our trucks are not rated near the big GM trucks in towing capabilities.
 

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2006 gmc envoy_slt_xl
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Discussion Starter · #5 ·
tow haul

It is a feature that raises the shift points and the pump pressure so the shifts are harder.. It does allow you to tow in od. But only after 65 mph and if your foot is not in it.. It is a good system that gm should of put on the envoys and tb.. My half ton has towed between 7500 to almost 9000 pounds with no problems and a 130000 miles.. Maybe someone needs to look at the electrical diagrams from both trucks and see what ticks... I am not that smart but a see a lot of guys and gals on here are...
 

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2009 chevy
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It is a feature that raises the shift points ...
That's exactly what is does, I just looked it up. And, overdrive is still available.


Maybe someone needs to look at the electrical diagrams from both trucks and see what ticks.
The electric diagrams will only show a switch and associated wiring (probably 2 leads).
It's done with programing in the PCM.
When the switch is operated, the PCM uses a different set of transmission shift parameters.

It could be done, but at what cost??
 

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2008 chevy trailblazer_lt
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35 Posts
The newer vehicles with this feature also have an active braking system that goes in tandem with the tow haul mode. When the tow/haul mode is activated, going down steep hills and things like that cause the transmission to shift to higher rpms to help slow the vehicle, or maintain a speed...it's kind of weird, but neat too.

Anyways, I've never seen anything that can give TVOYs this same feature...might involve a lot of monitoring systems.
 

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2009 chevy
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The newer vehicles with this feature also have an active braking system that goes in tandem with the tow haul mode. When the tow/haul mode is activated, going down steep hills and things like that cause the transmission to shift to higher rpms to help slow the vehicle, or maintain a speed...it's kind of weird, but neat too.
.
That is engine braking.
Your going downhill, your foot is off the gas, the transmission downshifts, the engine revs come up.
The engine revs up, not because your giving it gas, but because the rolling vehicle is causing the engine to turn.
The compression in the engine acts like a brake, holding the vehicle from rolling too fast.
Good feature.
 

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2003 chevy trailblazer_lt
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its the greatest thing i have had when i was towing a man lift in my old silverado... the tow/haul button also worked great in low traction areas... never spun tires in rain or ice when ever i had it on even with out a load...
 

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2004 gmc
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its the greatest thing i have had when i was towing a man lift in my old silverado... the tow/haul button also worked great in low traction areas... never spun tires in rain or ice when ever i had it on even with out a load...
And yet another formerly articulate member has his comma, apostrophe, and SHIFT keys abducted by aliens and held for ransom.

:rolleyes:
 

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2005 chevy
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The tow haul button is exactly that...doesn't let you use overdrive, but gives you 4th gear.
I would also like this feature, and would be a perfect addition to my setup for the times that I tow. If I got that, and maybe a pcm upgrade I would consider getting a camper again before going to a pickup...
 

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2005 gmc envoy_sle_xl
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hmmm :undecided waiting on my pcm to return, had them set it up for towing so i wonder how that will work
 

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2006 gmc envoy_slt_xl
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Discussion Starter · #17 ·
You dont have to if you give it to much gas it will stay in third... You can put it down in third so it does not hunt when going up and down hills... I think we just find out where to run the wires to the bcm and then alvin can do some programing and woolaa your trailvoy has tow haul.. Sound easy dosent.. Well i can dream...
 

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2007 chevy trailblazer_ls
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480 Posts
I would LOVE to have a tow/haul button! I believe that all the button does is gruond a wire comming out of the pcm that says "when this wire is grounded run this shift prgram " I don't think that we have the pin comming out of the pcm to ground, if we did maybe it would be possible to do this.Can a tuner who has done both chime in and set all of us straight? One thing that I have noticed is the truck seems to learn that there is a boat back there. After I unhook the boat the truck shifts great-for a short time then goes back to how it was before I hooked up the boat in the first place. Jay
 

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2009 chevy
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I would LOVE to have a tow/haul button! I believe that all the button does is gruond a wire comming out of the pcm that says "when this wire is grounded run this shift prgram " I don't think that we have the pin comming out of the pcm to ground, if we did maybe it would be possible to do this.
You are probably right, most automotive switching is the ground. Reason: if there is a short, the worst that will happen is that something operates.

The pin is likely there, we probably don't have the program.
 
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