I've tryed looking in the for sale sections, and can't seem to find what I'm looking for. Does any of you have a 3.55 or 3.73,8 lug, disc,rear end that you would want to sale or trade for a 4.10, 8 lug disc?

 

need more info, I believe the only gear ratios for the Ram were 3.73 or the 4.10 up until this year when AAM started making the rear axles for the duramax those are available in more ratios

paul

 

My goal is to save some fuel. I have the 4.10 right now.

 

It may help if everyone knows what year truck you are talking about as the newer trucks have AAM and older ones have Dana IIRC.

 

Couldnt you just do a ring gear and pinion swap to a higher gear? Lot cheaper than buying a whole new rear end.

 

Ahhhhhh, I'm gonna throwthe saying about gear ratio swaps for fuel mileage out there again......

Changing gears for fuel economy is like getting a Diet Coke with a Double Whopper Meal..........it just doesn't have the desired effect.

Basically, you are looking at around a $600 - 1000 for a 2X and double that for a 4X.

You can buy a LOT of fuel for that, let alone make up the difference in what you'd realistically see.

The only time that changing gears is necesary and economical is to restore performance with lift / tire size changes or to increase towing. Otherwise, you'll be throwing money down the drain.

 

01, 2500, 4x4

 

Ive got 4.10's and at times I do wish I had the 3.73's, however even with 4.10's 19mpg is possable

 

I know some people that are getting mid 20s mpg without being chipped. They have 3.73s. I get 20+ mpg with several mods and a light foot.

 

Both Dodge and GM believe
that the number of mph/1000 rpm
is important to Diesel economy.

That is why ex-GM foundary American Axle
(which was taken private by ex-Chrysler managers laid off by Daimler after the Daimler/Chrysler merger)
is developing new differential gears for the 10 and 12 bolt diffs.

Ex-Chrysler VP, and now GM head of design,
Bob Lutz ordered American Axle to come up with the 3.42 ratio that is now used in the base GM pickups this year.

Any diesel owner can see for themselves what rpm effect there is on mileage by simply doing test runs in 3rd gear, then do the same stretch of road in 4th gear.

Those diesel owners with GearVendors Underdrives installed can even further experiment this way:

http://dieseltruckworld.tenmagazines...e&aid=2798

sample quote:
"Would you believe me if I told you that a full-size, diesel powered pickup can get 30 miles per gallon while being driven at 75 miles per hour? Like you, I might believe it, but I would still want to see some proof with my own eyes."

There is a interesting Society of Automotive Engineers Journal paper from about 25 years ago where they installed two Laycock underdrive units in a row on a gasoline vehicle's drivetrain behind a manual 4 speed trans
(this gave them 16 speeds)
then did testing at various speeds and engine rpms.
MPG improved up to ratios of 40 mph for every 1000 rpm.

Now the new Tundra 6 sp auto has a top overdrive ratio of 0.59 with 4.10 rear differential ratio. (I will let you figure out the mph/k-rpm with 29 inch tires, it is worth the effort)

Cummins also has given their official word on how engine rpm affects fuel economy, and they say keep the rpm low:

http://www.cummins.com/na/pdf/en/pro..._Whitepape.pdf