Tow/Haul mode operation

[kenandterry]

Maybe I'm not using it right, or don't understand it's operation.

I have been experimenting with the transmission a few times out, and when I have the cruise control engaged, BUT I DO NOT have the tow/haul feature activated, I find the transmission WILL STILL downshift at LEAST one gear if the motorhome starts to pick up speed on the down side of a hill. I assume this is because the cruise control is trying to maintain the selected speed, and it cannot apply the brakes, and gravity is causing the motorhome to go faster.

I'm guessing the same thing would happen if you do NOT use cruise control, and without using/riding your brakes, you activate the tow/haul at this time to help slow the motorhome down.

Can someone explain the procedure to use if I'm wrong? In hilly countryside, are you supposed to leave the tow/haul activated all the time? How many gears can/will the tow/haul downshift?

Thanks

[jsutherl]

In cruise control the trans will down shift to maintain the set speed on down hill runs. This happens with or without tow haul on. I don't know of any way to disable this.

With tow on and cruise off the trans will down shift when you ride the breaks for more than a few seconds. It will up shift again when you push on the gas gently for a bit.

With cruise off and tow off the trans will only down shift when the engine speed gets too low (lugging out) or you push the throttle almost all the way down (passing gear.)

The computer will limit the throttle and/or change gears to prevent you hurting the engine.
For example: when you're going down hill in cruise the trans will down shift to prevent over speed, but not so far that it will drive the engine over red line RPM. And it will shift back up if the increasing downhill speed drives the engine close to red line RPM.

What is the red line RPM? I don't know. Most aluminum block engines like the ones we have have a variable red line. The red line is much lower when the engine is cold. As the engine warms the red line increases. At any rate the big V10 engine in our motorhomes makes such a god awful racket at high RPM that I've never let it get high enough to see where it limits.

[cfsoistman]

jsutherl covered it very well. I can only add that you will get use to the downshifting with Tow?Haul engaged. I recently traveled up to Altoona PA from just outside of Baltimore. Some of the hills on Rte 70 are pretty severe but the coach stayed under control while towing my Grand AM. On occasion it went up to 4200 RPM but most of the time it stayed around 3500 RPM on the downside. The noise doesn't seem as bad as I remember from beginning or I've lost some of my hearing??