Duramax Torque Management

ShinerBock wrote:

transamz9 wrote:


I know it locks when accelerating because that is the spot that I don't like on my trans towing heavy. When I take off it shifts to second pretty quickly. It then locks up and if I don't give it quite of bit of fuel it will go to third and stay locked. Second to third is a big jump and a lot of times won't get the job done. So when I take off I will mash the go pedal pretty hard until I get into 3rd then back down.

Believe me, it locks in 2nd-6th.

You ain't lying about 2nd to 3rd gear jump in the Aisin. Going from a ratio of 2.00 to 1.34 is a big leap, and probably drops the rpms down quit a bit requiring a mash of the throttle like you say. The 68RFE, which is geared almost identically to the Allison 1000, is only a 1.84 to 1.41 leap.

Although, the stock 68RFE programming is not as good as the Allison in my opinion which makes a huge difference on how the truck drives and accelerates in stock form. Whoever tuned the 68RFE at the factory seriously needs to go learn from Allison. A good trans tune for the 68RFE from a reputable tuner will fix this though.

Yes, it is a huge jump when you throw in 3:42 differential and 34" factory tires. It's really kind of hard to explain but let me give you a little example where it aggravates me the most.

When we are going through a town where there are multiple stop lights and I take off from a light like a normal person towing 20,000# behind them would my truck will shift (in TH mode) right around 2,000 rpm. Taking off like this is normally a little slower than regular traffic allowing me time to let off for the next red light and not have to get on the brakes hard. When I take off like this it shifts 1st to 2nd then a second or so later will lock the converter which is fine but it will then shift to 3rd keeping the TC locked. If there is any incline at all the truck will nearly fall on it's face basically holding the speed at which it shifted into 3rd instead of continuing to accelerate through 3rd. I then have to give it more go pedal in turn making it shift back to 2nd (rather hard sometimes).

If I take off hard enough for it to run the rpm up to 2,500 then it will shift smooth as silk and have no trouble with power. The bad part about that is that with 3.42 gearing and 34" tires I am right on the rear bumper of the car in front of me running with traffic that has the ability to stop a whole lot faster than me. Rolling hills on the back roads also cause the Aisin confusion in second and third. I've seen my rpm get as low as 1,100 in 3rd gear before it would shift back down to 2nd with my foot on the floor. It's not just this current truck either. My last truck was a '13 with the same gear and trans. It did the exact same thing. Make any sense?

What I usually will do in situations like this is manually shift it between 2nd and 3rd. I will manually hold second until around 2,500 or so before I shift it to 3rd if I want to drive easy. If not I just hammer down until it gets to forth and then back off. LOL