Is the Allision tow/haul mode GREAT or what!

[Penngrovian]

Went up into the mountains to about 7000 feet with the 4000 lb. slide-in camper in the bed. Going downhill was 900% better than the 01 F350 with A/T that we sold. The Ford brakes would heat up promptly on a 6% grade.

The Silverado required little or no braking and we felt much more safe coming down the mountains.

I occasionally would drop the tranny into 3, 2 or 1 to see what wuld happen and did not notice any internal downshifting as when in "D".

The rpm's never got higher than 2500 in any mode as a brake application would cause a downshift when in "D".

There was no info about downhill Allison shifting in the Chevy owner's manual or in the Allison video. Are there any tips out there for me?

Thank you.

[johns]

Having just finished a 3800 mile trip pulling a 12,000 # 5er I have a few observations that may or may not contradict what Penngrovian noticed.


1. Going downhill the truck would pick up speed. Once I stepped on that brakes to slow down a bit, the trans downshifted to keep me at that speed. On the most part it worked, but there were occasions where I would pick up speed again. Stepping on the brake a 2nd time caused another downshift again keeping me at the desired speed. There was one downgrade in particular where the trans downshifted and the engine was at 3500 RPM, I was still picking up speed and I had to apply brakes fairly heavily and more frequently than I would like, to slow down.

2. I noticed that when going up an incline, I would loose about 5MPH before the trans would downshift. It takes a while to pickup that 5mph pulling 12,000 #'s uphill.

3. There were times when going up an inlcine that the trans would downshift, as expected. But after going over the crest of the hill (even though I was either on flat ground or now going downhill) the trans would not upshift again. I thought that maybe the computer was keeping in a lower gear to avoid searching. But, on more than one occaision, I went a few miles without the trans ever upshifting again. I had to take it out of TOW/HAUL mode, the trans would upshift and then I put it back into TOW/HAUL mode again.


Anybody else experiencing this?


Penngrovian: The main rule of thumb I've ever used towing is to use the same gear going downhill that I had to use going uphill.

[ 11-12-2002: Message edited by: johns ]</p>

[Penngrovian]

johns:

Your para. 1 and our recent experience seem to be the same.

Para 2, I was not paying attention to going up hill.

Para 3, I noticed what you experienced but if I hit the accelerator and speeded up a bit, the transmission would up shift, even if in tow/haul.

I am new to Duramax/Allison and hauling a 4000 lb camper in the bed and learn a little each time out.

I would guess towing a 12,000 5er would affect the Allison a little differently than my truck camper.

Thanks for the reply

[Black Dog]

1. The Allison can only do so much to keep the truck/trailer from picking up speed. Once that threshold is passed, brakes is all you got. Just be glad that these trucks have really good brakes (especially in comparison to a SD).

2. So many people bitched about shift busyness on the '01s, that GM reprogrammed the tranny to let it slow down like that before a down shift.

3. They seem to do that sometimes. I believe it is part of the programming to try to eliminate shift busyness.

[johns]

Black Dog

I kinda figured they programmed the trans tha way to eliminate shift search (constant up and down shifting) as that will tear up an auto tranny. I just wanted to see if others experienced the same.

As far as speed control downhill, I'm happy with the trans. I know there will be times when I will have to use the old fashioned brakes ;) ;) . I think the trans did a great job hold me back going downhill.

Thanks for your input.

[ 11-12-2002: Message edited by: johns ]</p>