Fuel mileage and auxiliary OD trans

[Lektrikman]

I see a lot of 3rd gen owners talking about poor fuel mileage. Anybody out there running an auxiliary OD trans? I've been considering a US Gear unit but they install their unit between the vehicle trans and the transfer case on the 4 WD trucks. I don't feel like modifying my truck that much and I'm curious if anybody has ever seen a US Gear unit mounted on the rear of the transfer case?? I had a Gearvendors unit once but wanted to try a US Gear unit, but it doesn't look like they make the right adapters. Thanks, Lektrikman

 

[WOT]

Good question - been wondering if they have something you can install post transfer case. Also, if anyone has any fuel mileage reports after an install.

 

[Matt400]

I think it will depend on your tire size and gear ratio.

If you spend allot of time at or above 2000 rpm then it may help but you can buy allot of fuel for what one of those cost.



I have found on my 03 and now same on my 05 is that 2000 rpm is the threshold at where mpgs start to drop considerably.

 

[J.BURCHFIELD]

I have a Gear Vendor which reduces RPM 500 at 70 MPH. It is nice to reduce the noise level but there is no difference in MPG. I have a 98 12v and put in Marine injectors which gave me 3 MPG better mileage while towing but the same as before not towing. Does not make sense to me either. -- email address removed --

 

[betterthanstock]

Keep in mind that even though your engine will save some friction/pumping losses, any extra gears will typically waste about 3-4% due to friction.

If you can avoid extra gears by going with taller tires or final drive ratio, that is better.

Also a freer exhaust, and intake, and synthetic oil will reduce the losses at higher rpm.

 

[COBRAJET]

I ran a gear vendors in a 99 Ford F350 4X4 CC with 4. 10's and got . 5 mpg better maybe. The same setup in an 03 dodge with a 6 speed netted . 5 mpg. It had 3. 73's. It is not a practical investment if mileage is all you are looking for.

 

[J.BURCHFIELD]

COBRAJET, I agree but less RPM on the engine will make it last longer and the noise level in the cabin is much less. I am glad I have mine. It does require maintenance which is no problem for a retiree. Maybe that is why I like diesel engines, lower rpm does not grate on your nerves as much. My 12v should last a long time. having 101K on a 98 is next to nothing. In another 8 years I may not have 200K and that isn't much for an engine that should go one million. REGARDS

 

[hsmith]

I have mine not for economy, but for splitting the gears when I tow. Hard to justify the cost for economy, but I would not be without mine as long as I tow.