Allison Tanny Tow/Haul Mode

ausdoug · July 8, 2002

I have only made 4 trips of approx. 200-250 miles each way pulling my 12K 5th Wheel. I've experimented a little with the Allison Tanny Tow/Haul mode button. I have the 8.1 engine on a 2500HD. I noticed that when I'm accelerating that the tanny stays in 4th gear (shift lever in OD) than when I don't use the tow/haul button.

I live in central Texas and it has some highways with rolling hills but no bit mountains to climb or decend. My question: Is it ok to not use the tow/haul mode. I didn't use it for much of my last trip and it appeared to run at a lesser rpm and I believe the gas mileage was a little better.

On various forums, the tow/haul mode appears to be the mode to be in if you are decending steep inclines.

I'd appreciate any comments from those who have towed heavy loads with and without using the tow/haul mode.

CMNTMXR81 · July 8, 2002

You don't need to use it, it's simply an algorythm (sp?) for the PCM to hold onto a gear for longer when pulling a load.

For instance, I use it when accelerating, once cruising I hit the button and run like normal

bluenote · July 8, 2002

You don't need to use it, it's simply an algorythm (sp?) for the PCM to hold onto a gear for longer when pulling a load.

Tow/haul also locks the torque converter in gears 2, 3 and 4, and, of course, activates the full grade-braking capabilities when needed.

I generally don't use the tow/haul at all. I haven't the occasion yet to tow down any serious grades, so I'll probably want to use it there when I do. In very hard, or heavy towing, you may want to use the tow/haul mode to help keep the tranny temps at a reasonable level.