Hi, as it says, "Tow / Haul" means when towing or hauling that is where the transmission should be. I agree with the short version from Fyrzow post #11 and the long version from BillTex post #12 .
As a Ford person I will admit that the GM Allison transmission is a great trans, But don't think for a minute that nothing can go wrong with it. Acrossed the street from where I work, at a local Ford dealer, is a Chevrolet dealer with a separate building just for Allison transmissions. Now they handle Allisons from all over, but on any day, I can go over there and see piles of bad Allisons lined up for repairs. Like any other brand, they can go bad too.
WE HAVE A 1995 SUBURBAN 2500 454. 4WD, 3.78 GEARS.<>BANKS POWER PAC,(HEADERS AND COLD AIR INTAKE),EXTERNAL TRANS FILTER AND TEMP GUAGE. MSD IGNITION UP-GRADE. JET-6PAC COMPUTER CHIP, LOW TEMP THERMOSTAT. THE RIG HAS BEEN TOWING SINCE NEW. I FEEL THE MOST IMPORTANT ITEM IS THE TRANS TEMP GUAGE!! TRANS TEMP STAYS BELOW 190 DEGREES WHEN TOWING ON THE FLAT IN DRIVE. WHEN THE TEMP STARTS TO CLIMB SHIFT INTO TOW/HAUL. IV'E GOTTEN AS MUCH AS 13.8 MPG.(in Kan.) 11.9 IN TOW/HAUL. ON A NORMAL TRIP TOWING MI. AVERAGES BETWEEN 9.3 TO 10.4 . AFTER 178000 MI. WITH TRANS. SERVICE EVERY 30K, WE HAVE HAD NO TRANS CONCERNS AT ALL.(except those damn cooler lines, leaking at the crimps every 60k). THE RELATIVELY SMALL MILEAGE IMPROVEMENTS SPREAD OVER 170000K ARE SIGNIFICANT.
ONE OF THE NICEST THINGS ABOUT THE AIRSTREAM IS HOW WELL IT TOWS.
REMEMBER: IF YOU HAVEN'T BEEN ANYWHERE, IT'S HARD TO MAKE A COMBACK!!!!!!!!!!!! BOB
Great discussion!
The T/H mode used by all manufactures is designed to change the PCM parameters when T/H is engaged. The new shift points provide additional torque (upon upshift), less slippage (clutches) and lower temperatures while accomodating heavier loads (ie; towing). In summation, reduced slippage and lower temps lead to longer tranny life and happier owners!
I use Tow/Haul mode only when towing our 25' FB in hilly/mountainous terrain.
As mentioned in BillTex's post, the DA manual states: Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of (GCWR). The Chevy Duramax has a GCVR of 22,000 which translates to vehicile and trailer combined weight of 16,500. The truck is about 6,700 and the TT fully loaded is 7,300 = 14,000, which is well under 75% of (GCWR).
The manual goes on to state: Tow/Haul is recommended only when pulling a heavy trailer or a large or heavy load. I suppose deciding whether or not to use Tow/Haul depends on how you define "a heavy trailer or large or heavy load." I choose to use 75% of GCWR.
I have experimented towing with and without Tow/Haul and prefer without. With Tow/Haul turned off, I have not experienced excessive downshifting/upshifting and have towed in +90 weather with transmission temp staying well within normal limits.
However, Tom (Stream1529) is pulling a 34' Classic S/O w/ GVWR of 11,500. That probably meets any trucks definition of a heavy load. If I were towing his 34' Classic, I'd be using Tow/Haul all the time.
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Mike & Joan
WBCCI #1521 New England Unit
07 25' International CCD FB
06 Chevy Duramax/Allison
I use Tow/Haul mode only when towing our 25' FB in hilly/mountainous terrain.
As mentioned in BillTex's post, the DA manual states: Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of (GCWR). The Chevy Duramax has a GCVR of 22,000 which translates to vehicile and trailer combined weight of 16,500. The truck is about 6,700 and the TT fully loaded is 7,300 = 14,000, which is well under 75% of (GCWR).
The manual goes on to state: Tow/Haul is recommended only when pulling a heavy trailer or a large or heavy load. I suppose deciding whether or not to use Tow/Haul depends on how you define "a heavy trailer or large or heavy load." I choose to use 75% of GCWR.
I have experimented towing with and without Tow/Haul and prefer without. With Tow/Haul turned off, I have not experienced excessive downshifting/upshifting and have towed in +90 weather with transmission temp staying well within normal limits.
However, Tom (Stream1529) is pulling a 34' Classic S/O w/ GVWR of 11,500. That probably meets any trucks definition of a heavy load. If I were towing his 34' Classic, I'd be using Tow/Haul all the time.
I am also well under the 75% for the D/A, but I find the engine grade brake feature invaluable so I leave TH on whenever I am hooked up.
I have experimented towing with the truck in TH and without at our usual towing speed (62-63mph) and the result is no difference in RPM or MPG so I go for the engine braking and just leave TH on.
If I towed faster maybe I would see some advantage in dropping the TH mode at speed, as far as RPM or MPG, but I am not really comfortable towing faster than 62/63 with a load behind me and my family in the truck, so it has not been an issue. I don't want to start the "speed" debate again, but in this part of the woods (New England), anything faster while towing is nuts...
Why would you want to sacrifice engine braking and not use TH?
Bill
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Life is Good-Camping all around New England
Good people drink good beer-Hunter S Thompson
Sorry Bob If The Cap's Offend You;; I Only Use Them To Make The Text Easier For Me To Read. As Far As The Tow Vehicle Goes It's Still Going Strong At 178000 Mi. So I Guess The Mileage Up-grades Worked....keep Stream'n
Towed a 31 Classic fully overloaded from NJ to Fl just arrived. We have Burb 05/6L 3/4 ton 4.1. I had the TV in TM it ran over 2100rpms and on the interstate in CControl I got 10.7 mpg on back roads i got 9.6mpg. On the way up there to pick up the AS and fully loaded with 2 other passengers I got 14.6mpg better by 1mpg i got empty running around town on the interstate out of TM. in the stop and go average in town w/o trailer is 11.5mpg.
The only hills we had were approaches to interstate cross bridges the CC would rev up the engine. I learned to take it out of CC did not like the rpms going over 3000. The sharpest incline was ironically coming into Jacksonville crossing the St. Johns bridge. What is the right approach upon beginning the declining aspect of the bridge?
Sorry Bob If The Cap's Offend You;; I Only Use Them To Make The Text Easier For Me To Read. As Far As The Tow Vehicle Goes It's Still Going Strong At 178000 Mi. So I Guess The Mileage Up-grades Worked....keep Stream'n
Hi, the other Bob is trying to help you. On my very first post, I did all caps and was slammed and put on indefinite restriction. [well it seemed like forever before I was considered a good citizen again.]
I, also drive the F-250 PSD with the Tow/Haul feature engaged most of the time when pulling the 23’ Safari. I, also, completely agree with BillTex’s preferred towing speed of 62-63 mi./hr!
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Hi, as it says, "Tow / Haul" means when towing or hauling that is where the transmission should be. I agree with the short version from Fyrzow post #11 and the long version from BillTex post #12 .
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