Peterbilt Automatic Allison Transmission Information Please?

I have been driving a Peterbilt with automatic transmission. I have only been driving trucks for maybe 2 months or so. The truck does not have an owners manual inside but I wanted to learn a bit about the automatic transmission. It is made by Allison. It has a box inside the truck with R N D buttons, and another button that has MODE written on it. As far as I can tell, MODE is for choosing between economy and performance mode. Does anyone have experience with this system? Is there a way to force the transmission to force shift into gear say if you lose the brakes? Any information on this transmission really appreciated.

 

Are the engine brake controls on the lever on the right side of the steering column? If so try pushing the lever up and down. Down to downshift and up to upshift.

 

You sure the mode isn't to allow you to shift it manually?

 

It could be if the company hasn't had that option removed.

 

Its an Allison and more than likely has this kind of selector:
All the mode button does is toggle between economy and performance. From what I understand, performance mode operates just like a regular car automatic. Step hard on the throttle and it downshifts. In economy it won't downshift on a hill if you step on it unless the RPM drags down below peak torque RPM.

If you want to manually downshift a gear, should just have to push the down arrow.

 

I don't think this one has that but I will take another look

 

I don't know. From what I read online it is an economy or performance selector.

 

That is the one! Thank you! Ok so it is possible to downshift by pressing the button. In an emergency ie downhill picking up speed,it may not be able to go into gear?

 

It depends on RPM. If the engine rpm will be too high it will not downshift.
I would decide what gear I needed to desend, slow and select the gear I needed.
It also worked well to limit upshifts.
You can arrow up or down at any time to limit top gear.
Mode button can be configured for different shift programs depending on application.
Play with the different settings and figure out what works for you. One thing about allisons is they are programmed to not hurt anything and save themselves.

 

Feels a lot better know at least a bit how these things work finally