Red Ron

I have an '07 2WD, 5.3 Crew with towing package & stabilitrak, and higher ratio rear end for towing. Question: When towing for about 500 miles recently I played with the tow/haul mode. Other than the light coming on I could not tell it made any difference. The trailer only weighed about 1500 lbs. This is the only time I have used tow/haul but I assumed it would hold me in 3rd to help going downhill but I couldn't tell it made a difference whether on or off.

bad2006z71

on my 06, it changes the shift paterns of the transmision and holds gears longer to help keep the truck from hunting for gears. i dont think it locks out OD, you just have to be going at a higher speed for it to kick in, say instead of 45 when OD kicks in, you have to be doing 60 or something. not really sure. i use it when im towing a car or when im going up the mountains in West VA while towing my ATV. it works well.

Red Ron

Thanks for the reply bad2006z71, i guess i was just expecting it to help hold me back and help with braking like older trucks I have had.

ChrisRod

I asked the dealer about that. Like Bad2006z71 said it does hold the gear longer. I just wanted to add its more for driveing around town with the trailor, or like he said going up the mountains. I usually use it around town and depending on the highway on ramp, sometimes getting on the highway and yes it does work good.

ukrkoz

well, i believed that T/H mode does shut down OD, but i was wrong. i re-read the manual, and in it - and on the web - it does say that T/H mode changes shifting points for transmission and has "added benefit of better towing performance in OD". so no, it does not disconnect OD, just shifts differently. manual says that it is not adviseable to use it for regular driving without load, due to "unpleasent shifting experiences". which, when i tried that, it kicks like and old mule while shifting.
T/H or not, in general, those trucks are made for WORK. very moment they are loaded, everything sounds/runs/shifts/suspends better, smoother.

racerx55

it will not help with braking at all. if you have the shifter in OD and the trans has only made it to 2nd or 3rd gear, when you let off the throttle it will free coast and come to an idle. that it the one part i really dont like about it.if you manually shift it then it will hold back when coasting.
T/H mode raises the linepressure and makes a harder and latershift to keep the trans from slipping & buring up the bands.
my 05 Z71 and 07 2500HD both act the same way with it on.

96chevy7.4L

The tow haul mode changes shift points however it also locks the torque converter up right away to reduce heat. It also increases line pressure in the transmission which reduces slippage in the clutches and reduces heat also. A word to the wise. IF you do alot of towing you want the transmission to shift as firm and as fast as possible. Always use the tow haul mode when pulling and put a shift kit in the trans. They are easy to install and save you alot of money in transmission repairs down the road. Also a massive transmission cooler and one of those Derale Cooling tube pans help tremendously. I only say this from experience.