My activation of grade brakeing doesn't appear to be working most of the time. I'm pulling a 14,000lb trailer. The dealer could not find any codes present and doesn't know what else to do. Does anyone have any ideas?

You need to be in tow/haul for it to work

:exactly:

Need to be in T/H!!!!

I am in tow-haul.

It should activate when you apply the brakes when going down a steep grade. Or the tranny should gear down when approaching a stop light.

You will know if it's working, definate difference over non tow haul.

So when not in Tow/Haul, it will work also, correct? Either that, or there's something wrong with my truck as it will downshift after the brakes are applied on a grade.

I believe grade braking is active all the time. My truck works that way anyway. Mine doesn't seem to downshift as often and quickly as I would like it to either.

My grade braking in T/H seems to only work in T/H. It will down shift when not in T/H but it will not hold there unless in T/H.

Mine works in regular mode. It engages when braking on a grade w/ my trailer (I dont know the exact criteria) and stays in the lower gear until I apply light acceleration. Just got back from vaca on Sat and it worked well coming down the passes. I have a 2002, not sure if they made any changes in the following years

Maulcruiser

I believe in non T/H it will downshift from 5th to 4th, much the same way as T/H but that's it. At least that's what mine does.

When in T/H, it is night and day difference, you would know it upshifting and downshifting.

I don't use it unloaded, when driving around town it rarely shifts to 5th.

My 06 only seems to do it in the T/H mode when I pull my 5ver although it does also downshifts if I leave the cruise control on and I am going downhill in order to maintain the speed. But to respond to original post, it is SUPPOSE to downshift going downhill when brakes are applied. Might want to check with an Allison dealer for more info.

My '06 also only seems to work in T/H. I found that I had to press the brake pedal for about 2 to 3 seconds, before the tranny downshifts. If I apply the brakes again in the same fashion, the tranny would downshift to the next gear. I found that I had better speed control by going into Manual and controlling the shifts that way.

I found that I had better speed control by going into Manual and controlling the shifts that way.

Us 06'rs made out on that one for sure. I use my manual regularly when coming off ramps... let those break pads take a rest. Nothing better thany being able to downshift at the press of a button... but still have the convenience of an automatic transmission. :D

Maulcruiser

I believe in non T/H it will downshift from 5th to 4th, much the same way as T/H but that's it. At least that's what mine does.

When in T/H, it is night and day difference, you would know it upshifting and downshifting.

I don't use it unloaded, when driving around town it rarely shifts to 5th.

Yeah, that's all it does, but unloaded that's all I need it to do to hold 55 MPH coming down the mountain. I did have to flip the T/H mode on when I had my trailer behind me because it was running away from me.

I was just curious if that was a lesser form of the programming of the TCM as opposed to something being wrong with the truck.

The downshifting I noticed happens so smoothly that unless your looking at the tach you wouldn't know it.