Using the "M" on the Allison Transmission - Chevy and GMC Duramax Diesel Forum
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old 05-18-2008, 01:36 PM Thread Starter
Join Date: May 2008
Posts: 1
Using the "M" on the Allison Transmission

Ok, I am new to the diesel truck and the Allison Transmission. I see that the M is used when pulling a trailer. My question is When is the most appropriate time to use this feature. I will be going to Colorado in June and will be crossing over Cinnamon Pass that drops into Lake City. I have been told by most folks that once you go down this pass you will not want to go down it again. I am thinking that this is purpose for this feature. I can use all the help I can get concerning towing my 5th wheel through the mountains and how this feature can help.


2007 Duramax LB with Old body style
No modifications at this time
Roughly 20,000 miles
Duramaxcop is offline  
Sponsored Links
post #2 of 9 (permalink) Old 05-18-2008, 01:39 PM
Super Moderator
BigRedChevy's Avatar
Join Date: Oct 2007
Location: Greenville, KY
Posts: 6,060
Most of the time Tow/Haul mode will do everything that you want it to do with the grade braking feature. If you wanting to put it in M mode to hold a gear longer then it wouldn't hurt a thing. The allison is a very smart tranny and will take care of itself, if you put it in M4 it won't let it over rev it will shift to 5 before it hurts anything, so i would say put it in tow/haul and take it easy at the top.

Welcome to the site!!!
BigRedChevy is offline  
post #3 of 9 (permalink) Old 05-19-2008, 07:12 AM
Junior Member
fenmor's Avatar
Join Date: Feb 2007
Posts: 46
M - is for manual

I tow a 5 th , and personally I dont find too many times that I need the manual control or the tow-haul mode .
Going through the mountains here in British Columbia , I will use the tow-haul mode when going up a very steep grade for some distance or use it when going down a steep grade where brakes alone may heat up.
You will love the Allison trany , its the only auto to have in a tow vehicle . ( or stay with a standard )
fenmor is offline  
post #4 of 9 (permalink) Old 05-19-2008, 07:28 AM
Save Water, Drink Beer
Landscapeman's Avatar
Join Date: Nov 2007
Location: St. James City, Florida
Posts: 1,102
I tow a large trailer most of the week and I have never had to use M. Tow/Haul mode takes care of everything. Good Luck and Welcome.

2006 GMC 2500HD LBZ Crew Cab 4x4, Tie Rod Sleeves, LineX, Silverline Turbo Back Dual Exhaust, PPE Hot Programmer, Egr Block Plate, PPE Air Box Mod, 2in. Plug, SES Light

Full Bore Exhaust Manifold compliments of BD Diesel.

1987 Corvette

Crazy Larry. Get it Here.
Landscapeman is offline  
post #5 of 9 (permalink) Old 05-19-2008, 07:36 AM
Senior Member
pONSi's Avatar
Join Date: Feb 2008
Location: bay area
Posts: 391
I was towing in "M" mode this past weekend...I used this mode in windy hilly roads where I knew my speed would be changing quite often...In my situation I felt there was no reason for my tranny to shift into 5th or 6th gear during this time because before I knew it I was decellerating down to 2nd gear so I set it in "M" 4...This just prevents it from shifting between gears so much which I think is easier on the tranny
pONSi is offline  
post #6 of 9 (permalink) Old 05-19-2008, 10:57 AM
Diesel Addict
Join Date: Feb 2007
Location: Barnesville OH
Posts: 7,756
the only time i used M mode is when i was running heavy roughly 25,000-30,000 pounds gross weight so on the hills i put it in M mode and shifted to 5TH gear to keep my EGT's down since i was running aftermarket HP.

Project, Rogue Budget(Workstock Puller)
2006 GMC 2500HD, Stock Motor, EFILive by me, Billet 63 VVT, Motorsport Stroker CP3, 20% Nzls, ProFab Manis n Uppipes, BD IC, Hot Pipe IC, ProFab Y-Bridge, lots of other goodies
post #7 of 9 (permalink) Old 05-21-2008, 12:31 PM
Junior Member
07blkLMM's Avatar
Join Date: Sep 2007
Location: Johns Creek, Ga
Posts: 91
Even though I have only towed my TT once, I used the M when I was decending a steep winding grade on a mountain road that I didn't want to get over 20 mph on. Otherwise, I just used T/H on the main roads. It works great!

07.5 Black Chevy Duramax LMM. Westin Nerf Bars, Undercover bed cover, otherwise stock.
07blkLMM is offline  
post #8 of 9 (permalink) Old 05-28-2008, 08:29 AM
DuramaxForum n00b
TomK's Avatar
Join Date: May 2008
Location: Sedalia Colorado
Posts: 13
I live in Colorado and tow my 5th wheel in the mountains allot. I've found the T/H works great 90% of the time, automatically down shifting and applying the engine break on the down hill side of the passes. I use the M mode on the steeper, windyer roads that I feel I need more control on. I've descended many long steep grades by toggling up and down through the gears without having to use my brakes. It makes for a safe and comfortable decent.
TomK is offline  
post #9 of 9 (permalink) Old 05-31-2008, 01:53 PM
Join Date: May 2008
Location: Huuto TX
Posts: 1
linzer truck lines inc
hotshottrucking is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Chevy and GMC Duramax Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome