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LI Pets · 06-13-2007, 06:22 PM

One quick example, 2 mile 8% grade, I was going faster than I wanted to, I tapped the brakes, got to 50mph and the truck went the whole 2 miles selecting the correct gear.

I didn't touch the brakes, other than the first time.

Cracker · 06-13-2007, 06:49 PM

They just keep improving the Allison - but even with my '03 I haven't got any complaints. It just requires a tad more imput from the driver (---touching the brake to make it shift when going downhill.) As for "Tow/Haul" mode, I use it anytime I'm towing the Airstream. Once you get over about 57 mph T/H is no longer a factor. When travelling in the flatlands, it still makes life easier on the engine and tranny by delaying the shift points - so I still find it to be beneficial. I get around 14 mpg towing and 18 to 21 solo - and I use cruise control religiously, except in the mountains.

Four years and 56,000 miles of nothing but pure enjoyment from the 2003 GMC Duramax/Allison!

ZoominC6 · 06-13-2007, 07:11 PM

The THM is always on when towing our Airstream. Love that Duramax/Allison combo.

Minnie's Mate · 06-13-2007, 07:45 PM

I have whatever transmission Ford put in the F-250 Powerstroke in '05...I know, I'm so knowledgeable about mechanical things. I put over 180K miles on my F-150 (never towed with it) and kept if for 12 years. I figure I'll keep this truck even longer so I don't want to wear it out prematurely. So whenever the Airstream is behind me, the tow/haul button is pressed. I just wished the idiot light to remind me it was on was a different color. That yellow light that reads "tow/haul" is distracting and makes me think something is wrong.

Why couldn't it be green like the cruise control light? Anyway, I would rather buy a few extra gallons of diesel every trip than a new transmission @ $3-$4K during the life time of this truck.

I will check my manual though because a good bit of my longer trips cover the flat lands between central Georgia and central Florida. My Airstream weighs 6,500 #'s dry and loaded I figure around 7,500 #'s and that is a little over half my truck's towing capacity. I do use the cruise on the interstate and every other chance I get.

stanton66 · 06-13-2007, 09:04 PM

i take it in and out of th to get it to shift into od when towing in a 55 mph
zones.the allison has no problem pulling in od. trans temps are always under
200.

thecatsandi · 06-13-2007, 09:06 PM

Whenever the Trailer is attached. no matter how short or mlong the trip even if it is around the hangar. They put it ther for a reason. My Classic is the only thing I have ever towed with it.

2 Winds · 06-13-2007, 09:20 PM

I use the T/H as often as I remember to press the button, which is most of the time once I get into the road routine. I would appreciate an idiot sensor on the hitch that turned it on automatically when a load was on.

Curious if anyone has ever overheated their trannie by not using TH.

I've had success with cruise on flat or rolling country (big, long prairie hills) by setting the cruise just a tad lower than desired speed. As I approach a hill I manually accelerate over the cruise set speed (to desired speed or a bit above) to avoid the drastic downshifts that cruise brings on. I'm not running a heavy load so I don't think cruise is hurting anything but wouldn't be the first time I was wrong.

What are the reasons for not using cruise?

Mileage is usually 10-14. Best mileage I got was late afternoon last summer in eastern Montana - 17 mpg. The air was cool and calm and I didn't want to stop. Rode right into the sunset.

Fyrzowt · 06-13-2007, 11:05 PM

I use the cruise all the time at highway speeds, unless I'm in hills.

ROBERTSUNRUS · 06-14-2007, 12:12 AM

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.

LI Pets · 06-14-2007, 05:06 AM

The only time I don't use cruise is if I'm a bit tired, don't want to do that Chevy Chase thing he did in "Vacation"

On some hills it downshifts a little early maybe, but when I'm driving say NY to Fla this toy is priceless.

ROBERT CROSS · 06-16-2007, 04:46 AM

GREAT TOPIC!!!

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

LI Pets · 06-16-2007, 06:18 AM

Hi Bob, I guess you're not aware that posting in CAPS is screaming and poor etiquette.

Anyway sounds like you have a hot rod not a TV

lsinclair · 06-16-2007, 10:46 AM

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!

hiker · 06-16-2007, 11:55 AM

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.

BillTex · 06-16-2007, 06:43 PM

Quote:

Originally Posted by hiker

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

LI Pets · 06-16-2007, 06:58 PM

Quote:

Originally Posted by BillTex

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.

Why would you want to sacrifice engine braking and not use TH?

Bill

I agree 110%

ROBERT CROSS · 06-16-2007, 07:23 PM

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

Rob30044 · 06-16-2007, 07:49 PM

I never use tow/haul mode. I tow mostly on level terrain.

chaimemet · 06-16-2007, 08:47 PM

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?

ROBERTSUNRUS · 06-17-2007, 12:01 AM

Quote:

Originally Posted by ROBERT CROSS

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.]