I do when it makes sense, like longer hills and when there is a good headwind. If I can keep the speed around 70 then it doesnt lug as bad and I can usually conquer the rollers if they aren't to long or steep. 6th is a good choice for long, flat stretches of freeway to save fuel.

 

the higher gear, the better fuel economy. If the temps are getting higher, that is most likely due to a lower water pump / cooling fan speed, then lugging the engine. The higher the rpm's the faster the fuel usage.

 

When I am climbing hills I will use the M mode alot to control the truck especially if I am following some jacka$$ who doesn't know how to use the gas pedal. I notice cooler exaust temps at times while in a lower gear if the truck is having problems at that speed even with higher RPMs

 

I would attribute your lugging problem to your increased tire size. I'll let you or others do the math, but I wouldn't be surprised if your larger diameter tires is affecting the ratio to where you are dealing with a 3.40 or perhaps 3.20 gears. Pulling a heavy trailer in 6th with that ratio would certainly be an issue.

 

Lugging the truck in a higher gear can also unlock the torque converter and cause it to generate additional heat. Dropping to a lower gear can usually use less of the torque converter or cause it to lock, allowing it to run cooler. Lugging the motor also builds heat more so than letting it use the lower gears to it's advantage. I agree with RV Guy in that larger tires may also be affecting your RPMs. Just my $.02...

 

keep it in drive, tow/haul on, and leave the damn thing alone! The allison was built to haul huge trailers day in and day out without rest. You do not need to second guess it or try to help it out.

When you are in tow/haul, the converter DOES NOT UNLOCK WHEN YOU LUG IT.

the allison is not the turbo 400 you had in your 80's K30. It is not like any other automatic, and it does not need to be treated as such.



ben

 

Thanks for the imput guys. Good point about the tire/wheel size. As for just leaving it alone and letting it lug I'm not to hot on that idea. Anytime that engine is lugging and and the boost is up is when the mileage takes a ****. I'm recalling a 400 mile round trip I made a couple weeks ago with a single axle enclosed bike trailer and one bike. Comming home we had a really good head wind and there was no way the truck was gonna pull in 6th efficiently. Usually when I pull though it's probably around 11,000 pounds with bobcat and trailer.

 

there was no way the truck was gonna pull in 6th efficiently..

so put the cruise control on and let it do its thing.


I dont know why no one beleives me. We need to stop trying to second guess these things. The dmax and allison are perfectly matched for eachother and this is what these trucks were designed to do. If you feel that you can make better decisions and handle things better than a state of the art 32 bit transmission computer then you should have bought a manual transmission, because shifting the allison manually and messing around with it will not help your mileage or towing efficency...

JMO!!

ben

 

Put a tune in it and you will gain mileage and it will pull 6th gear all day long. EFI live is your friend...

 

Yeah, stick in 6th "manually" and set the cruise at 80 and watch the Allys fall behind .
On topic do you guys see the egts go through the roof with your Allys went towing 25K in 6th ):h?

 

There is no way in hell I want my vehicle to decide when I'm to close to a car.