Duramax owners

camper1999 · 05-10-2015, 10:41 AM

I just learned something that some of you might have already figured out but I thought I would pass it along. I just got back from a 2,000 mile round trip towing my Silverback fw. I like to tow right at 65 mph. I noticed that my trucks rpm was close to 2000 rpm. I found if I brought my truck up to around 68mph briefly and then back off to 65mph the truck shifted to another gear and dropped my rpms to almost 1500. Saved me some diesel and thought I would pass it along.

hbillsmith · 05-10-2015, 11:06 AM

Nice to know but do have some questions. Were you in Tow Mode? What is the mileage you get when towing vs. not towing? I have a 2015 version of your truck and a Wildcat 295rsx which I think is comparable or even slightly lighter. I get 19 avg no tow and range 9 to 10 when towing.

camper1999 · 05-10-2015, 01:01 PM

I was in tow mode. I was getting close to 12 mpg on that trip. But I average 11-12.5 most of the time. Not towing on the highway I get 20-22 mpg. I use to get only 8 mpg with my Gasser towing less weight

asquared · 05-10-2015, 01:25 PM

Quote:

Originally Posted by camper1999

I was in tow mode. I was getting close to 12 mpg on that trip. But I average 11-12.5 most of the time. Not towing on the highway I get 20-22 mpg. I use to get only 8 mpg with my Gasser towing less weight

This is where my mpg runs as well. I have a 12000 lb full profile fiver when towing. Only do some mountain towing and I always tow in tow mode with exhaust brake on.

retiredguy · 05-10-2015, 01:30 PM

Quote:

Originally Posted by camper1999

I just learned something that some of you might have already figured out but I thought I would pass it along. I just got back from a 2,000 mile round trip towing my Silverback fw. I like to tow right at 65 mph. I noticed that my trucks rpm was close to 2000 rpm. I found if I brought my truck up to around 68mph briefly and then back off to 65mph the truck shifted to another gear and dropped my rpms to almost 1500. Saved me some diesel and thought I would pass it along.

I find that when in tow mode on cruise, if it shifts down, it will not shift back up to overdrive. Thus the rpm's stay around 2000. I usually wait for level stretch and take it out of tow mode. It will then shift up so the rmp's are around 1500. Once this happens, I put the tow mode back on.
Not sure if this is good for the truck, but it's good for mileage.

bulldog4949 · 05-12-2015, 10:29 PM

I tow about 65-68 with my 5'er. I have it in tow mode and the exhaust brake on.

If my truck shifts to 6th on flat land, I put it in manual and tow in 5th gear. This is the best for mpg with my style of driving and rig.

Maybe this is what its doing with you.

larryo · 05-13-2015, 04:23 AM

When you take her up to 68 then slow down you are shifting into overdrive. I can only comment from a dodge prospective, but the 68re dodge transmission is very similar to an Allison. The shaft your 6th gear is on is about the size of your little finger. Pulling a load at 1500 rpm is really lugging both your engine and transmission which is really not the best in the long run. Ideal rpm for a Cummins is around 1800. Put it in drive with tow switch on. If she pulls up to overdrive fine, if not then don't force it into overdrive. If it goes into overdrive but does a lot of shifting just manually go to 5th and leave it there. Think of it this way.....if it doesn't shift up to overdrive she is telling you that she doesn't want to be there!

GaryanJane · 05-13-2015, 05:30 AM

we have a 2009 silverado 3500hd xlr dually. i always use tow mode when pulling our 5er. my question is how do you engage or use the exhaust brake ?

TURBS · 05-13-2015, 05:59 AM

Quote:

Originally Posted by GaryanJane

we have a 2009 silverado 3500hd xlr dually. i always use tow mode when pulling our 5er. my question is how do you engage or use the exhaust brake ?

Gary I can't remember for sure but 09 "I think 10 was first year" didn't have an exhaust brake.

However my 08 didn't either but when I had my truck tuned they use the vvt as an exhaust brake.

When I'm in heavy to mode "tune" and in tow mode "shift lever" I build about 8 lbs of boost while braking acting as an exhaust brake.

Clear as mud?

TURBS
08 duramax tuned n modded, 32bhok Sabre
2015 camping "4 nights"

DreiHunde · 05-13-2015, 06:02 AM

Thanks for passing along the info!

I just set the cruise at 60 and let the beast run where it wants!

Pipeman · 05-13-2015, 06:32 AM

In tow mode, the shifting pattern stays in the gears longer and therefore will shift at a higher speed and rpm. I've owned 2 duramaxs now and have driven both this way; depending on terrain I drive in regular mode until I reach the speed where I'm in 6th gear, usually around 62mph. I then switch to tow/haul. My exhaust brake is on all the time. If I have to brake then tow/haul mode and exhaust brake really slow the TV & 5er down. I also have cruise control on and set for 66 mph.When driving in hilly to mountainous terrain, I'm in tow/haul mode. When the TV shifts down to 5th because of a hill and then gets to level ground I will take it out of tow/haul mode so the transmission will shift up to 6th and then I put it back into tow/haul mode. I have a 2011, 1 ton dually crew cab, long box, 4x4 pulling a 35 ft CC 5er. My 1st Duramax was a 2001, 3/4 ton, short box, 4x4, crew cab pulling the same 5er as I have now & before that a 36 ft TH. It was was overloaded on the GVWR but as some salesmen would say "it will pull, no problem" and it did. I do watch my tach and also can hear when the transmission shifts. I usually get between 9 - 12 mpg when hauling, again depending on terrain and wind and I have seen up to 23 mpg in the city depending on the length of the run before lights etc. It's always up and down in the city. It's a learning curve.

DFW Rusty · 05-13-2015, 07:22 AM

Quote:

Originally Posted by GaryanJane

we have a 2009 silverado 3500hd xlr dually. i always use tow mode when pulling our 5er. my question is how do you engage or use the exhaust brake ?

I have an '08 and neither of our trucks have the engine brake.

I put it in Tow Haul mode on just about any trailer I pull! Tow haul isn't just for high speeds in the mountains, it holds gears longer on take off so you don't work the tranny too hard. It also helps when coming to a stop by down shifting for you and letting the tranny wind up the engine to help stop the truck better.

If I only kept a truck for a couple years after new then I would probably do the same as most of y'all, but I'm not going to risk damaging my tranny over a few more mpg! I like to see around 400k on my trucks before I get rid of them.

richp · 05-13-2015, 07:51 AM

Hi,

I have an '09, with no exhaust brake, towing a Silverback 33RL that weighs in at about 12,500# for most of our trips.

I put it in tow/haul when I fire it up, and leave it there the entire time. My view is that the engineers know better than I how to optimize towing performance within the limits of the equipment. That's not to say what others do is wrong, or necessarily hard on the equipment, but I'm an inherently conservative guy, so I go with a more sedate use pattern.

I hold my highway speeds right around 60 mph; this general method of use gives me a pretty predictable 12 mpg towing.

FWIW.

Rich Phillips

clr · 05-13-2015, 08:18 AM

I tow a 12623 lb dry 5th wheel with my Ford F350 and I have noticed the same thing. I always tow in tow mode and drive about 65 top speed. I have noticed if it down shifts for a hill or you have to slow down for any reason that some times it will not shift all the way up and the rpm will be higher. So I do just like you step on the gas to about 68 mph it will finish up shifting and then I let the cruse take over. I think that 65 mph must be about the shift point when towing my load. This does not happen very often to me but seems more likely when towing into a head wind or similar. I have to remember to look out for this happening when towing.

rsscully · 05-13-2015, 06:10 PM

If you want the trans to shift back to overdrive sooner why not turn off the tow/haul mode so it won't hold gears as long?

SuicideSaints · 05-13-2015, 06:40 PM

Quote:

Originally Posted by camper1999

I just learned something that some of you might have already figured out but I thought I would pass it along. I just got back from a 2,000 mile round trip towing my Silverback fw. I like to tow right at 65 mph. I noticed that my trucks rpm was close to 2000 rpm. I found if I brought my truck up to around 68mph briefly and then back off to 65mph the truck shifted to another gear and dropped my rpms to almost 1500. Saved me some diesel and thought I would pass it along.

Isnt it just up shifting to 6th? Defeating half the purpose of tow haul? Why not just use tow haul (for the longer shift points) till you are over 55 then shut it off, essentially the same thing and still towing in 6th.

I have a dodge and it does not like less than 1700 rpm when towing (i thought all diesels wanted between 1800 -2200 for optimal performance).

I dont know any of this for fact but this is what I do, I never tow in 6th and i dont tow less than 1700 rpm (except accelerating to cruise speeds).

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