? on Proper Use of Tow/Haul Mode

lauriet1 · April 22, 2002

I towed my loaded horse trailer this weekend (about 4,200 lbs). Got to test my 2500HD up and down a REALLY BIG HILL! My old 'burban would be doing about 20-25 mph at the top of this same hill and I would be holding my breath wondering if I was going to make it. NO PROBLEM for the new truck...I was doing 50 mph at the top and had plenty more if I needed it....I'm very pleased

Going Down the same REALLY BIG HILL, I put the truck in Tow/Haul at the top. It downshifted, rpms went to about 3,000 and wouldn't come out of that gear, until I turned the Tow/Haul Feature off and even then it took longer than I would have expected to for the shifiting to correct itself.

I'm betting this is "user error". Would someone out there like to provide an overview on the proper usage of the Tow/Haul Feature? I did a search on Tow/Haul and didn't find anything. My apologies if this is a redundant topic. Thanks much!

hosspuller · April 22, 2002

Doesn't sound to me as if you did anything wrong or the truck either. Don't know about the standard auto transmission, but the allison in T/H will down shift to slow vehicle if brakes are applied. Sounds like your trans downshifted (3000 rpm engine speed is normal). It won't upshift in T/H until you get on the throttle and your road speed demands a shift.

Jpshostr · April 22, 2002

Just engage the tow/haul mode in when you start out and forget about it. No need to engage and disengage it while on the road. You may want to manually shift the truck into 3rd out of OD when approaching a hill rather than wait for the truck to lug down and shift itself down.

lauriet1 · April 22, 2002

Thanks for the input! I do have the allison tranny and didn't realize that when in Tow/Haul, the truck would shift into OD. I thought that T/H mode was the same as driving the truck in 3rd gear. Guess I was wrong on that one. Also nice to know that 3000 rpm is okay. Sure sounded funny though. I suppose it will just take some time to get used to my new toy. After driving 350 Auto Suburbans for the last 10 years, (never in overdrive while towing), I'm sure this baby is quite different! I'll also do the old RTFM routine tonight.