Chevrolet integrated brake control

[Wingeezer]

Originally Posted by catson4

Wingeezer - Technically the "M" stands for "Range Selection Mode" but has been and probably will into the future be called the "MANUAL" mode.

"AIRSDREAM" wrote:
{The Allison transmission's also got "manual shift" mode that uses the little + and - buttons on the stalk to select gears. To access it, just move the gear selector until your readout says "M-1" or something like that. Using that, YOU select the gear with the + and - buttons, and it won't shift out of it unless you get quite high engine speeds or come to a near stop. I sometimes use this when moving heavy loads like a tractor on a trailer, at low speeds over uneven ground where I'm looking for constant low speed and I don't want it to change gears on me.}

Actually the read out on your dash will say from left to right ; P-R-D-M-1,
If you select the "M" then you are in "manual" mode. If you select "1" then you are in low gear and the trans will not shift up.
As Airsdream says then you select the gear you want, up or down, using the rocker switch on the gear shift lever, as indicated with the + or - signs.
HOWEVER, the trans WILL shift down on it's own ,at it's pre-set shift points, IF you select ANY range ABOVE first.
In other words, if you select 3 and come to a stop light with out shifting up or down, The trans WILL shift down for you. Then when you start moving again, the trans will shift up from 1st through 2nd and into 3rd range as your speed and RPM's dictate but it will not go above that . You will have to shift it up or down OR move the selector lever to D and that would put you back into regular drive.
You can shift between Drive & Manual at any time.
If you are running on a level highway at 60 mph in Drive, you can shift into Manual and the display on the dash will show you are in 6th range.
In the "M" mode then you can shift down and the display will show which range you have selected. If you shift down to many ranges and the trans is not ready to take that range, it will decelerate until it can shift into the selected range. This is not a recommended shift as you will be putting the Duramax RPM's right at the top of each range as it shifts down.
Not good IMHO.

The manual mode works in either "Regular" or "Tow" modes.
It really works great on slippery roads as you do not need to brake as often because you can slow down with the trans and it is smoother than brakes.
And it is super in the mountains and even on the freeways. I use "M" when towing and set it to 5th range. that way the trans does the shifting as it needs BUT does not go into 6th and I get better MPG as the motor gets to use the fuel it is being fed rather than running at the lowest RPM in 6th. This works with my 34ftr and I have just over 21,000 miles in 16 months on my "07 Chevy now.
In 5th range I get right at .5 to 1.0 miles per gallon MORE than in 6th on the freeways running at 60 MPH.


Drive it a while and , like "MIKEY"-you will like it.

Thanks much!

Your explanation gives much more detail than the info in the GM manual!


One thing I did not in the manual however - if I read it correctly - is that when in tow haul mode, the transmission has a grade-braking feature, bgut if you select M, (even if in tow/haul) you cancel this feature.

If that is so, then I presume you would not want to be in "M" on long downgrades?

Thanks again for taking the time, its very helpful! ........ Brian

[66Overlander]

To clear things up, there are at least two types of "manual mode" that can be applied to automatic transmission vehicles.

One type allows you to directly select the transmission gear (e.g. "3" = 3rd gear). These types will hold the selected gear as long as the engine rpms are within acceptable ranges, but if holding the gear would cause an engine stall, they will generally downshift. Likewise if holding the gear will over rev the engine they will generally up shift.

The second type allows manual selection of transmission range, or maximum gear (e.g. 3 = 1st thru 3rd gear range). In this case the transmission shifts normally within the allowable range, but will generally only upsihft beyond the range if the engine is going to be over rev'd.

Sports and touring cars typically use the first type of "manual mode" (gear select). Trucks, including those equipped with Allison transmissions, generally use the second type of "manual mode" (range select). There may be exceptions both ways.

[catson4]

You are correct, the grade braking can only be put into operation in "TOW MODE".
And the Grade Braking works great on LONG down hill runs.
The Westbound lanes of I-90 on Snoqualimie Pass in Washington, from the summit down hill for about 4 miles, is a good example. And the Siskiyu Pass on I-5 at the Oregon / California border.

Unless the steep grade is more than a few miles long , I find the "Manual" mode better. But that is just personal preference.

Enjoy your clean burner.