jls
canastota, ny
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What exactly what does turning on the tow haul function do. It is very vague in the owners manual. Quite frankly my truck seems to tow better with it off.
john and Pam
2006 Chev K1500 Z71 4x4 5.3L
2002 Sunline Solaris T-2553
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downtheroad
Puget Sound
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Joined: 02/18/2003
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On our Allison tranny T/H changes the shift points. Basically holds the tranny in each gear longer (higher RPM's)
Tow Haul helps keep your tranny from "hunting" and thus will keep it a bit cooler. Also when in T/H the "Grade Braking" feature is engaged.
Whenever we are hooked up, I put it in tow haul.
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jim87vette
Arizona
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downtheroad wrote:On our Allison tranny T/H changes the shift points. Basically holds the tranny in each gear longer (higher RPM's)
Tow Haul helps keep your tranny from "hunting" and thus will keep it a bit cooler. Also when in T/H the "Grade Braking" feature is engaged.
Whenever we are hooked up, I put it in tow haul.
What he said.That grade braking will really wake you up though when the motor hits 4k kinda got my attention,but I realize it will not hurt the motor.
08 GMC 3500 Dually Duramax
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ktosv
Allendale, MI
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The 1/2 ton gas (and even non-Allison HD?) trucks do not have the grade braking.
As was mentioned. It changes the shift points and keeps the engine in it's power band. I do all of my towing with it on as the truck makes the decision as to what gear and when. I even used it this weekend towing a small low profile utility trailer.
If I recall correctly, with the exception of starting from a dead stop or coming to a complete stop, it keeps the RPMs above 2000. Basically, each shift point has been modified so that after the shift the engine is running over 2000RPM. This in essence eliminates any HP or torque lag from dropping below the powerband and having to build back up to it.
My previous two tow vehicles ran the same tranny as my Burban but didn't have T/H. In my opinion towing with T/H is a drastic difference and improvement.
Kevin and my...
Wife, three daughters, a son
and two dogs(brittany and english setter)
2005 Suburban (295HP/335#-ft, 3.42 axle)
1994 Caprice LT1 (260HP/330#-ft, 2.93 axle)
2003 Trail Cruiser C22
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Jim&Peg
Central Ohio
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Joined: 07/14/2004
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The other difference with at least some transmissions it that tow/haul will keep the torque converter clutch locked up most of the time. This reduces heat buildup in the transmission.
It is designed to optimize performance/life of components when towing. Why would anyone not use it as designed?
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havedreamwilltravel
Southern California
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Quote:The 1/2 ton gas (and even non-Allison HD?) trucks do not have the grade braking.
Our 1/2 ton has the grade braking.
Works awesome. Usually slows us down so well we hardly use the brakes going down grades.
We always tow with the tow/haul mode on!
2007 GMC Yukon Denali - 6.2L 380hp/417ft-lbs,0-60 in 6.2 seconds
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Classic Hammond
Milwaukee Wisc.
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In TH mode my Yukon appears to not want to shift into 4th gear running closer to 3000 RPM. Kicked off the 8.1 settles into 4th around 2200-2300 rpm @60 mph. I may be incorrect but I assume my mpg would improve. I think the powerband is between 2 and 3 thousand.
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JIMNLIN
Big Cabin, OK
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Joined: 09/14/2003
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Jim&Peg wrote:The other difference with at least some transmissions it that tow/haul will keep the torque converter clutch locked up most of the time. This reduces heat buildup in the transmission.
It is designed to optimize performance/life of components when towing. Why would anyone not use it as designed?
more rpm doesn't equate to better towing performance/better mpgs/etc for all drivers. Its a great feature for rookie truck operators that don't know what gear to run in or when the TC clutch is locked/unlocked. This type of discussion comes up on ocassion on some of the hotshot type forums for commercial haulers I'm a member of. These folks are on the road daily and towing max axle loads. Many GMC/Chevy/DMAX/Allison operators have found they have less fuel usage by turning off tow/haul mode.
My Dodge truck is a 6 speed manual 2wd but on ocassion I use my wife's 4x4 truck with tow/haul mode to pull my trailer/tractor/mower/box blade to a muddy work site. I to found the tow/haul mode keeps the engine at high rpms when on county roads or stop and go traffic in city areas. Tow/haul is not for every.
Jim
'03 2500 Dodge/Cummins HO 3.73 6 speed manual Jacobs
'97 Park Avanue 28' with two slides
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shutdown
In The Dog House
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Joined: 03/13/2008
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I use mine on county roads. As others have said it holds each gear longer on both up and down shifts. the real disadvantage i have found to it is that it will NOT let it into 4gear till about 65mph. when on a flat road crusing at 60 there is NO reason not to be in 4 th gear...which is when i turn mine off.
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JIH
Albuquerque NM
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Joined: 09/30/2007
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"On the average" those who tow heavy, without using tow/haul mode will wonder why they need transmission work at 80 to 100K miles. Those who use tow/haul as recommended will "on the average" get many more miles before they need transmission work. Just like buying insurance, some of us need to follow the recommendations of the multitude of engineers the manufacturers employ. Others who know everything will never follow anybodies recommendations.
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