Allison Trans discussion

77GreenMachine

Phillip Talton
Joined
Mar 30, 2010
Location
Trinity, NC
For the sake of discussion...

Talking with a buddy about buying an 05’ 8.1/Allison truck. I shared my only experience with an Allison which is this:

03 Duramax (LLY), towing a TJ to Harlan. In Tow mode, if I was going down hill and got on the brake just a little to slow down and I just rode the brake for a little to maintain speed the Trans would gear down, which I know it’s supposed to do. But several times it geared down to the point of red lining the truck. Since I was unfamiliar with this, it scared me and I didn’t want to hurt the truck so I would give it gas and it just redlined it more, so I’d scramble to get it out of tow mode.

My question is:
(1) was it ok to rev that hard?

(2) Was it my fought for “riding the brake” like I was?

(3) does the Allison behind the 8.1 gas engine have the same characteristics as behind the Duramax?
 

Mac5005

Well-Known Member
Joined
Oct 19, 2005
Location
Rocky Mount
For the sake of discussion...

Talking with a buddy about buying an 05’ 8.1/Allison truck. I shared my only experience with an Allison which is this:

03 Duramax (LLY), towing a TJ to Harlan. In Tow mode, if I was going down hill and got on the brake just a little to slow down and I just rode the brake for a little to maintain speed the Trans would gear down, which I know it’s supposed to do. But several times it geared down to the point of red lining the truck. Since I was unfamiliar with this, it scared me and I didn’t want to hurt the truck so I would give it gas and it just redlined it more, so I’d scramble to get it out of tow mode.

My question is:
(1) was it ok to rev that hard?

(2) Was it my fought for “riding the brake” like I was?

(3) does the Allison behind the 8.1 gas engine have the same characteristics as behind the Duramax?

In tow mode, I’ve had the 6Lxx do the same thing. I’ll usually opt for manual mode and use the selector button once I get off flat ground.

Not sure the total difference in programming between the Allison and 6l series, but I’ve had the exact same experience.

Tow haul mode being too aggressive on downshifting in breaking. One thing is to down shift early to stay off the brake pedal and use more compression braking.
 

77GreenMachine

Phillip Talton
Joined
Mar 30, 2010
Location
Trinity, NC
I haven’t had that problem with my 6.0/4L80. I do pull it down in 3rd on rolling hills for that help. The selectable shift didn’t come out till 11’ I believe.

Probably what I should have done with the Allison, but I just let tow mode do it’s thing.
 

Mac5005

Well-Known Member
Joined
Oct 19, 2005
Location
Rocky Mount
I haven’t had that problem with my 6.0/4L80. I do pull it down in 3rd on rolling hills for that help. The selectable shift didn’t come out till 11’ I believe.

Probably what I should have done with the Allison, but I just let tow mode do it’s thing.

I believe the manual shift selector started in 07/08.

The 4spd tow haul programming is much less aggressive than the 6spd.

My 4L85 would never downshift on braking in tow haul.
 

CarolinaHD

Well-Known Member?
Joined
Dec 2, 2008
Location
Mt. Pleasant NC
1. Yes
2. No
3. Yes


GM moved the red line on the gauge clusters starting in 2006 because of this same issue; customers were concerned/complaining/freaking out because it went over the red line.

Duramax cuts fuel at 3200rpm and can rev up while engine braking to 4800rpm.

Not sure about the 8.1

Manual mode for the Allison started in 2006.
 

Tim C

Wizard
Joined
Jan 22, 2007
Location
Fayetteville
As long as no aftermarket tuner has been installed, I don't believe they would allow a tune that would allow the engine to grenade itself. Especially if they are providing a warranty on that engine.

Fwiw my dad has complained about his 06 dmax reving high on downgrades in tow haul mode, I told him the same thing and said to let it do it's thing.
 

upnover

Grumpy, decrepit Old Man
Moderator
Joined
Mar 20, 2005
Location
Morganton NC
I have a 02, 8.1 and an Allison. The tow haul part doesn't work. But it still gears down. Maybe not as aggressively as you describe. But it does gear down. That, along with my trailer brakes, I have no issues of over revving or going too fast. Coming down Old Fort Mnt, I can keep it between 55-60 with ease. Most of the time, I just pull it down out of over drive.
 

77GreenMachine

Phillip Talton
Joined
Mar 30, 2010
Location
Trinity, NC
I have a 02, 8.1 and an Allison. The tow haul part doesn't work. But it still gears down. Maybe not as aggressively as you describe. But it does gear down. That, along with my trailer brakes, I have no issues of over revving or going too fast. Coming down Old Fort Mnt, I can keep it between 55-60 with ease. Most of the time, I just pull it down out of over drive.

Those models are really bad about the shifter pinching the yellow wire for the Tow Haul button. If you remove the plastic on the lower portion of the steering column (just a couple screws) you can see the yellow wire. Just splice it back together and you’re good to go. I have fixed 3 of them so far!
 

Croatan_Kid

How's your hammer hangin'?
Joined
Nov 4, 2007
Location
New Bern
An 03 is still an LB7. They downshift because they don't have a VGT turbo to help as an engine brake. They also have an anti coast clutch that helps keep the truck from gaining excessive speed when you're not on the throttle.

I couldn't imagine hauling anything heavy without the tow/haul working...it's sooo much better when the converter locks in second and stays locked.
 

77GreenMachine

Phillip Talton
Joined
Mar 30, 2010
Location
Trinity, NC
I couldn't imagine hauling anything heavy without the tow/haul working...it's sooo much better when the converter locks in second and stays locked.

I agree! @upnover for such a simple fix, better check it out. You’d be much happier with the towing if you think it does fine now.
 

skyhighZJ

Thanks for your taxes
Joined
May 31, 2012
Location
Aberdeen, NC.
Where is the tow/haul switch on my G56 Cummins?
Can't find that bitch anywhere
Yours is more complicated to activate.
1.) depress left foot pedal
2.) maneuver right hand lever thingy device to a position of lower numerical value as seen at the top of said lever thingy
3.) release left foot pedal to upright position
4.) repeat as necessary.
 

a_kelley

mechanical fixer
Joined
Jan 26, 2010
Location
Rutherfordton
Where is the tow/haul switch on my G56 Cummins?
Can't find that bitch anywhere
this g56 transmission is so advanced, it's mind controlled. It changes when your brain tells your hands and feet exactly what changes to make and when. It needs no tow/haul switch to accomplish any of the users desired results. Exactly what the user envisions, is accomplished merely by thinking about it.
 

CasterTroy

Motarded
Joined
Mar 21, 2005
Location
Wallburg
And just like that, cummings superiority enters the thread

images (3).jpeg
 

jeepinmatt

At least half the people are dumber than the rest
Joined
Mar 24, 2005
Location
Stanley, NC
Fun fact: The LB7/LLY Allison 1000s have a 6th gear that is not utilized by GM. Might also be true for the 8.1s.
 

Croatan_Kid

How's your hammer hangin'?
Joined
Nov 4, 2007
Location
New Bern
The 8.1s do too. The conversion isn't really worth it when you break it down. The price has come down some, but it's still pretty damn expensive.
 

jeepinmatt

At least half the people are dumber than the rest
Joined
Mar 24, 2005
Location
Stanley, NC
The 8.1s do too. The conversion isn't really worth it when you break it down. The price has come down some, but it's still pretty damn expensive.
I'm still unable to comprehend why they would have a transmission that was mechanically equipped with 6 speeds, but only utilized 5 :confused:
 

77GreenMachine

Phillip Talton
Joined
Mar 30, 2010
Location
Trinity, NC
I'm still unable to comprehend why they would have a transmission that was mechanically equipped with 6 speeds, but only utilized 5 :confused:

Go ahead and do all your R&D, engineering and production cost, flood the market and sell like crazy with the 5 speed. Design is already done so you change a couple parts and programming after a few years and flood the market all over again for all the folks that just HAVE to have that 6th gear!

Pure speculation on my part.
 

Croatan_Kid

How's your hammer hangin'?
Joined
Nov 4, 2007
Location
New Bern
It would be sweet if I had 6th on my truck and geared it 4.10 with the 33s. I'd get better low end and still have the same final drive as I do now. 5th is .71 and 6th is .61.
 

shawn

running dog lackey of the oppressor class
Administrator
Joined
Mar 13, 2005
Location
Raleigh, NC
I'm still unable to comprehend why they would have a transmission that was mechanically equipped with 6 speeds, but only utilized 5 :confused:

If it's like the Fords, you conceptually have a 3-speed reduction gearbox mated to a 3-speed overdrive gearbox. The final drive gear ratios are created by different combinations of front/rear gear, but there are actually up to 8 possible combinations (assuming there's a 1:1 ratio in both boxes).
 

NickMaul

Well-Known Member
Joined
Jul 4, 2009
Location
Norfolk, VA
I'm still unable to comprehend why they would have a transmission that was mechanically equipped with 6 speeds, but only utilized 5 :confused:

Chrysler did that with the auto behind V8s in the WJ. I think you could have the dealer do some re programming to get the extra “gear”


Sent from my iPhone using Tapatalk
 

Jody Treadway

Croc wearing fool
Moderator
Joined
Mar 20, 2005
Location
Hendersonville, NC
Chrysler did that with the auto behind V8s in the WJ. I think you could have the dealer do some re programming to get the extra “gear”


Sent from my iPhone using Tapatalk
Yup.
The very early 545RFE gained an additional gear in between D and OD so when you kicked it down it had an appropriate ratio so it wouldn't lug or scream.
Was just a simple PCM flash
 
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