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Old 02-18-2019, 04:20 PM   #1
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Ram 2016 3500 6.7 Cummins

I recently bought a 2016 Ram 3500 dully with the Cummins 6.7 diesel. It is equipped with the stock 6 speed trans. I believe I read somewhere that when towing my 13k Keystone Sprinter I should lock out 6th gear. It is supposed to keep it in the proper power band and therefore get better fuel economy. Does anyone do this and does it help with fuel economy?
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Old 02-18-2019, 04:37 PM   #2
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It does not help mine with fuel economy. There is a reason to gear down and that is to keep the engine in the power band (1700-2000 rpm). Used on the flats gearing down is not necessary. Expect mileage between 8 and 13 but there are a lot of factors. Speed and headwinds being a couple that will kill mileage.
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Old 02-18-2019, 04:40 PM   #3
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Turn on the Tow Haul Mode and let it do its thing
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Old 02-18-2019, 06:03 PM   #4
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If you check the owners manual, you'll see that tow/haul does not lock out overdrive. Tow/haul changes the shift points. When I had a 5er, I set mine in tow/haul and put the engine brake on "auto". Enjoy the new truck.
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Old 02-19-2019, 07:50 AM   #5
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I recently bought a 2016 Ram 3500 dully with the Cummins 6.7 diesel. It is equipped with the stock 6 speed trans. I believe I read somewhere that when towing my 13k Keystone Sprinter I should lock out 6th gear. It is supposed to keep it in the proper power band and therefore get better fuel economy. Does anyone do this and does it help with fuel economy?
We tow a Road Warrior 427 (empty 16K, loaded 19500) we have a 2017 RAM 3500 dually I use the tow/haul in the mountains and it helps going into the hills and down out of them. When we hit flat ground, coast areas tow haul comes off. Fuel mileage is around 9-10 mpg goes up a little on flat ground maybe another 1-2 mpg not much more then that.
Mountains we have towed in are the Smokies, later this year it will be out west area.
What rear end do you have and which transmission are you using?
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Old 02-19-2019, 10:14 AM   #6
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I leave the tow/haul mode on any time I am towing larger than a 20ft boat.

The longer the torque converter spends between locks means heat in the fluid. Especially with heavy loads the transmission needs to shift quickly and the converter needs to lock to keep the fluid temps down.

I would suggest never towing something heavy while not in tow mode.
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Old 02-19-2019, 10:31 AM   #7
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By stock trans I assume you have the 68RFE automatic? That is a very stout transmission.
For longevity, every time you start it turn on the EB. The only time it should be off is under low traction situations.
There is a button on the endmof the shift lever. If towing turn on tow/haul. Non towing on or off is totally up to you. It will make little difference in the way the truck drives. Learn where your torque curve is on the motor. When pulling im the hills use the gear selector to keep the RPMs in or near the middle of the torque curve. DO NOT let the motor lug down. Its almost the worst thing you can do for a diesel.
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Old 02-20-2019, 09:32 AM   #8
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By stock trans I assume you have the 68RFE automatic? That is a very stout transmission.
For longevity, every time you start it turn on the EB. The only time it should be off is under low traction situations.
There is a button on the endmof the shift lever. If towing turn on tow/haul. Non towing on or off is totally up to you. It will make little difference in the way the truck drives. Learn where your torque curve is on the motor. When pulling im the hills use the gear selector to keep the RPMs in or near the middle of the torque curve. DO NOT let the motor lug down. Its almost the worst thing you can do for a diesel.
Driving with the exhaust brake on kills the gas mileage on my 2010 as every time you let off the gas, it slows down the truck and gives you very little coasting time.
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Old 02-20-2019, 09:36 AM   #9
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Driving with the exhaust brake on kills the gas mileage on my 2010 as every time you let off the gas, it slows down the truck and gives you very little coasting time.
You are correct. I have never understood driving with the EB on all the time, even when empty. There is virtually no coasting time.

The newer rigs like mine have a 2 stage EB. One setting is a speed maintainer and the other is full stop. Even the first setting gives you very little coasting time.
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Old 02-20-2019, 10:30 AM   #10
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OK to really answer your question the only time I lock out 6th gear is when I tow in the mountains with the 68RFE auto. This way I am at the top of the power curve between 1,800 and 2000RPM's, although full torque is developed at 1200RPM's. Why this is to keep the EGT's below 1300F when I am towing in the mountains with my truck. This also will speed up the engine RPM's to provide more fan cooling to the cooling components when the fan is turning at engine speed and engaged. I like to keep my transmission temps measured from the oil in the pan below 185F when towing.
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Old 02-20-2019, 10:31 AM   #11
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You are correct. I have never understood driving with the EB on all the time, even when empty. There is virtually no coasting time.

The newer rigs like mine have a 2 stage EB. One setting is a speed maintainer and the other is full stop. Even the first setting gives you very little coasting time.
My exhaust brake is on 90% of the time. What little fuel mileage I may lose is more than made up by the brake pad life I save.
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Old 02-20-2019, 12:27 PM   #12
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My exhaust brake is on 90% of the time. What little fuel mileage I may lose is more than made up by the brake pad life I save.
Sorry Jim.

If we use 60k life for brake pads and 15miles a gallon and $3 per gallon

If you lose 1 mile per gallon that cost you $750 in fuel.

if you save 10% or even 20% in pad life and a brake job is $1000 on your truck. You are losing $550 in fuel costs.
Cost per mile for brakes is so far below cost per mile for fuel you will never make it up by using less brakes.
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Old 02-20-2019, 04:14 PM   #13
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Sorry Jim.

If we use 60k life for brake pads and 15miles a gallon and $3 per gallon

If you lose 1 mile per gallon that cost you $750 in fuel.

if you save 10% or even 20% in pad life and a brake job is $1000 on your truck. You are losing $550 in fuel costs.
Cost per mile for brakes is so far below cost per mile for fuel you will never make it up by using less brakes.
Will your assumptions are a little incorrect for my truck!

I had my first brake job on the front axle at 72+K miles for $375. The rear brakes were done at 99+K miles for $400. My fuel mileage for non-towing highway is between 19 and 21 MPG with the brake on. When towing in the tow/haul mode and brake is engaged (100%) my fuel mileage is between 10 and 12MPG's. With wind resistance being the biggest factor on my fuel mileage. City/town driving average is 13 to 14 MPG's. This is what others have reported when not using the Exhaust braking feature of their turbo charger on the Dodge/Ram trucks.

You lose more fuel mileage do to the regeneration process than you will ever lose with the exhaust brake use of the turbo charger.

Another benefit of running the exhaust braking feature on the VGT is longevity of the sliding Actuator from soot build up. That will lead to a costly replacement of the turbo charger. This is do to lack of exercising the sliding vane mechanism in the VGT when the exhaust brake feature is not used.
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Old 02-20-2019, 08:53 PM   #14
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Sorry Jim.

If we use 60k life for brake pads and 15miles a gallon and $3 per gallon

If you lose 1 mile per gallon that cost you $750 in fuel.

if you save 10% or even 20% in pad life and a brake job is $1000 on your truck. You are losing $550 in fuel costs.
Cost per mile for brakes is so far below cost per mile for fuel you will never make it up by using less brakes.
I'd be more worried about the cost of not stopping fast enough, or not at all.
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