6.7 Cummins with 68RFE - what gear you tow in?

estesbubba wrote:
I ordered my truck a week ago which means I have too much time to think about things. With my 2006 5.9 and 48RE, I would just put it in tow/haul mode and it would cruise down the interstate in overdrive most of the time. With my 2015 6.7 and 68RFE, should I just do the same using tow/haul or also limit it to the first OD (5th), or what?

My fifth wheel is about 10K lbs. and 2006 had 3.73's and 2015 has 3.42's.

Put it T/H and turn on the exhaust brake and go. I only downshift when going down or up steep hills while towing. Our 5'er is 12,600 dry.

The truck will pick the right gear for you in normal or tow haul mode but with 6th being a deep overdrive, I'd keep it in 5th gear tops and save the trans a few or a lot of downshifts.
RPMs don't hurt these engines. Lugging the engine is not good for it though and if you drive by the egt you will see how much cooler the post combustion temps are at higher rpms.
Vehicles are made pretty idiot proof but those functions are not always the greatest for longevity.

When towing my 5er and boat, I am about 17000 pounds towed weight. I put it in drive and let the computer shift. Sometimes I use tow/haul, sometimes not. My main complaint about that mode is it automatically begins down shifting every time I go to coast. Sometimes I dont' want that.

I have an app (car minder) where I track the miles. gallons, MPG, and fuel price of each fill up. My computer reading is usually very accurate. My 03 would read up to 3 - 4 MPG optimistic. Not the case with my 2012.

On a lighter note, the two things many truck owners seem to exaggerate are their MPG and the speed at which they can pull the passes fully loaded.

Cummins12V98 wrote:
Running with cruise on when approaching a grade let's say in 6th and you know you will be downshifting it's more fuel efficient to downshift your self instead of it dropping a couple MPH then the computer downshifting.

It gives you something to do when towing and your eyes can see what the computer can't!

Agree

Running with cruise on when approaching a grade let's say in 6th and you know you will be downshifting it's more fuel efficient to downshift your self instead of it dropping a couple MPH then the computer downshifting.

It gives you something to do when towing and your eyes can see what the computer can't!

estesbubba wrote:
I ordered my truck a week ago which means I have too much time to think about things. With my 2006 5.9 and 48RE, I would just put it in tow/haul mode and it would cruise down the interstate in overdrive most of the time. With my 2015 6.7 and 68RFE, should I just do the same using tow/haul or also limit it to the first OD (5th), or what?

My fifth wheel is about 10K lbs. and 2006 had 3.73's and 2015 has 3.42's.

I have the 6.7 with 68RFE and 3.42 as well. Just put it in tow/haul and set the smart exhaust brake on and you should be good.

FWIW - I tow a bumper pull that is around 12-13k loaded up steep grades into the mountains all the time when I am camping and I've never had to lock out any gears. Just enjoy it when you get it!

estesbubba wrote:
Thanks for the tips. So how reliable is the computer MPG and instant MPG on these trucks when stock? I know adding a tuner will screw them up but no plans on doing that for now.

For the life of my truck (About 70 fill-ups), I average a 3% optimistic error rate.

estesbubba wrote:
Thanks for the tips. So how reliable is the computer MPG and instant MPG on these trucks when stock? I know adding a tuner will screw them up but no plans on doing that for now.

My 11 was .4 high all the time.

Just filled the 15 in sig. Hand calc 14.63 and computer said 14.9. But who knows how full each tank were. It will take several tanks to average it out since these new trucks are a pain to get full.

The tank mentioned was stop and go on the freeway with city driving along with 60 and 70 freeway driving.

estesbubba wrote:
Thanks for the tips. So how reliable is the computer MPG and instant MPG on these trucks when stock? I know adding a tuner will screw them up but no plans on doing that for now.

They're not called Lie-O-Meters for nothing:).....Best way to figure out mpg is fill to same place each time, (when pump cuts off), then hand calc MPG....I got better mpg with the 2012 than the 2010 and I get better mpg now, then with the 12', but it's because of the DEF. also have the Aisin in the 13'...but 68RFE with DEF should also get better mpg....from all I've read, when towing, there really ISN'T that much difference when towing heavy between 3:73 and 4:10...3:42 works a little harder, MPG isn't as good.

retispcsi wrote:
My 2012 1 ton dually had the 68re and a 4:10 I towed a 36 ft. Cedar Creek fiver. I took the truck through the Smokey out to Denver and through the windy hills of Texas and Oklahoma. I left it in "D" with the tow haul and exhaust brake on. The transmission took care of all the shifting and never had an issue. It will in part depend on your rear end but you are pulling a light unit so that is a plus.

EXACTLY!!!!!