You driven Volvo?

M- manual shift, works good with mountains, holds the selected gear going down it so it won't be in to higher gear with less RPMs for these newer style engine compression brakes, just play with it, won't take long to find the gear for the speed/rpm combination to go down a mountainside

 

You can take hills in D just fine. They're actually really good trannys as far as autos go. One thing to keep in mind though, is they will upshift going downhill if the engine brake is not on. So don't count on engine braking without the Jakes

 

Difference between hills and mountains

 

M is good to have, holds a gear all day in the mountains. We had a rockwell auto that had a M mode for that. It seems we spent half our mountain miles in that manual mode. The trick is shutting down for one hour each week, which was pretty hard to do with a team truck. If you did not flush that buffer with a shut down, it will brick on you and require a tow.

 

I pulled a tank based out of idaho. Did all the Rockies a few times in it, loaded at up to 105,500. It'll be fine.

 

I had a T660 Kenworth with an actual gear lever. You had to Bring the lever into M (Manual) and could downshift with the up or down buttons. It held Donner real good heading west, and that is a long grade. With the Jake on and it in M Mode. You could still give it throttle without it trying to upshift like the Volvos do. Or so I heard. It would hold that gear regardless.
But, it was an AutoShift, not a full Auto. Meaning it had a clutch pedal. I did not care for it personally.

 

What happened to the Porn Star?