Towing with an Allison Transmission

[illahee]

I am asking for input from the Duramax and Allison, GMC and Chevrolet users when towing a trailer. My 2011 GMC 3500HD has the trailer tow package.
Do most of you tow in the automatic mode with the trailer tow enabled or do you tow in the manual mode. If in the manual mode do you used 6 or a lower selected as the highest gear.

Thanks for any input.

Illahee

[RCrawler]

The Allison is pretty good at picking the right gear for most situations. There are times when you can switch to manual if you feel that the transmission is hunting for gears or just doesn't feel like it wants to pull. Once you get the feel of where your D-Max's RPM sweet spot is, you will figure out where you might want to drop a gear or shift up.

You should have no problem running in 6th while towing on flat ground. Depending on your trailer weight and the grade, it might drop to 5th in auto.

Jason

[66ken]

I use automatic with tow mode enabled. I have forgot to turn on the haul mode and never noticed much difference. There is enough power there to just set the cruise and relax.

[campingcpl]

I have an older truck and it only has the 5 speed and doesn't offer the manual option but have never had a problem with towing. I use the tow/haul mode and usually don't turn the overdrive off unless in an area where the transmission starts down shifting or hunting for a gear.

I wish mine did have the manual option and the extra gear. Wanted a manual transmission when looking for a truck but wasn't able to find one in the price range I wanted to spend.

[RCrawler]

There is a kit that can retrofit a tap switch on the shifter for manual control on the 5 speeds. Also offers an option to control the lockup converter function. http://www.fleeceperformance.com/pro...b75bac6a3.aspx

Jason

[campingcpl]

Originally Posted by RCrawler

There is a kit that can retrofit a tap switch on the shifter for manual control on the 5 speeds. Also offers an option to control the lockup converter function. http://www.fleeceperformance.com/pro...b75bac6a3.aspx

Jason

That would be nice but don't think the DW will let me spend $520.00 + just to be able to shift the truck manualy. Not sure I want to spend that much either. Would rather spend the money on one of the turbo brakes personally. Thanks for the link and the info.

[jq1031]

The tow mode does all the shifting for you & at the correct RPM's. Use it that's what it's there for!

[ktmracer]

Originally Posted by illahee

I am asking for input from the Duramax and Allison, GMC and Chevrolet users when towing a trailer. My 2011 GMC 3500HD has the trailer tow package.
Do most of you tow in the automatic mode with the trailer tow enabled or do you tow in the manual mode. If in the manual mode do you used 6 or a lower selected as the highest gear.

Thanks for any input.

Illahee

Ours is the older 5speed allison. The only time I do anything "manual" is to turn OD off on some hills. mostly because if the road has tight curves, I'll tend to slow down enough to go to 4th, then accelerate into 5th, the slow down.... In those cases I just turn OD off and keep it in 4th.

Otherwise I just let the "tow/haul" mode do it's magic. I'm only towing 9,000lbs, so it isn't much of a workout for the duramax/allison combo.

[illahee]

Thanks for the advise to my question. I have been using the auto mode with the trailer tow engaged and it seems to work well.

[Vidorcom]

I tow in auto with my duramax in tow/haul mode. I do use manual when on a steep grade to assist with braking. The truck will still override in manual if it feels it's not the right gear. I never have used 6th gear while towing.

[cfite]

if your in manual your engine braking system won't work i don't believe.

[Vidorcom]

I use the manual for braking on my own. I'll down shift to keep the speed I want. I did just purchase a banks brake and iq I just have not installed yet.

[mhs4771]

With the newer Chevys & GMCs, turn on the exhaust brake, engage tow/haul, get up to cruising speed, set the cruise, sit back and enjoy the ride. The cruise brake feature will keep you from gaining too much speed on down grades, if you put in in manual mode it disables the cruise braking feature. Pulling 14K plus with ours and not a single problem.

[Vidorcom]

With icy roads in the nw I don't use the cruise control.

[Railcop345]

Many interesting comments but I have another one. Have 2007 with Duramax. I usually tow in trailer mode, even on the hills. Truck seems to have lots of power and not much gear searching. However, I was looking to add a chip for more power. While doing this, I placed the trans in manual and tow mode. Wow, lots more power. I did need to manually place the trans in 6th prior to starting unless I wanted to do the shifting, which I do not (reason for the automatic!). I have not pulled the trailer yet to check this out but all this to ask: Is this okay? will it damage the tranmission? Is this normal or did the previous owner modify something?

[LittleJoe]

In most cases you will find that your fuel mileage is better in 5th than 6th if pulling any significant weight with the DMax.
Also if you are going to lay down any significant power via chip upgrades, and are towing heavy in the hills you might want to make sure you are in 4th (direct) for this.

[christopherglenn]

1st through 4th are rated for ~950 lbs of torque, 5th & 6th are rated closer 700. At 660 stock it doesn't take much of a tuner to "limp" 5th and 6th. Most allison/tuner related failures are on the 4/5 shift at high throttle.