Does anyone know where or how I could change my 3.73 rear axle to something higher for better mileage? I do not pull a lot, and live on flat land. I would like to see my RPM drop to 1800 or below to gain better mileage. Or do they make a add on overdrive splitter to attach to the allison to give me more options? Any input would be nice! thanks. I would think with all the high priced fuel some one would invent a way to lower our RPM and gain some fuel mileage with these trucks. I don't want to drive around at 45mph, don't get me wrong, just think that we can get better mileage with a few changes to either the tranny or the rearend..:help:

If you're a 2wd a gear swap is fairly easy. I think the 3.42 is available. There was also an overdrive unit in the For Sale forum. Add you truck info in your signature when you get time. That will help the members help you!:)

My Truck Is A 4x4, Are There Vendors Out There For The Upgrade. Thanks

......but I'm with ya on the better mileage, not just because of high fuel prices, but just for the sake of not wasting fuel. I would think that a 2 speed rear axle of some sort would be the berries for when your running empty or slightly loaded. I don't need to lauch like the space shuttle from a dead stop everytime I take off.

The problem with the gear change on the 4x4 is that you basically have to change front and rear both. The Overdrive is pricey, but will probably work best for you. Either way it will take several thousands of miles to make up what you spent. Might want to consider playing with some other options. There are some that say exhaust, air intake, and chips can help. Do a search and you can read for days!):h

The 3.73 axle ratio is all there is for the duramax. You can buy aftermarket gears but they are all lower ie: 4.10, 4.56 and so on. I look about a year ago and someone else look within the last few months and came up the same way I did.......... nothing that fits.

I just wish someone would come up with something, this cannot be that difficult to do. Either a quick rearend gear change, or a splitter.. Let's research this and see what we can come up with. thanks

Just get bigger tires