Ratio Change

[Paw John]

Has anybody concedered changing out the front and rear diff. gear ratio on a F350 dually from 3:10 ratio to 3:73 ratio. I owned a 2001 F250 with 3:73 ratio and was making 18 MPG on the Hwy and 16MPH pulling my 36ft Mobile Suite. I now own a 2002 F350 4x4 dually with 3:10 gears and not getting good fuel mileage. It's getting around 12.5 mpg pulling my camper, 15 mpg in town driving and about 16 mpg on the high way. I was just thinking that if the cost of the ratio change is worth the future MPG savings. I'm thinking the cost would run about $ 1000.00 per diff. and I could do the work myself.

[RVThere]

Best way to look at this is financially.

Currently at 12.5 mpg, you are burning about 800 gallons of fuel to go 10,000 miles. At $3.75 per gallon, that costs you about $3000.

At 18 mpg, you burn 555 gallons to go 10,000 miles which costs you about $2083 at $3.75 a gallon for fuel.

So in rough terms, you save about $1000 in fuel for every 10,000 miles traveled.

So if this differential change costs you $2000 in parts (since you will provide the labor), you have to drive 20,000 miles BEFORE you start saving money in fuel. If fuel goes down in price, you have to drive more miles before you save money. If fuel goes up, then you realize your savings sooner.

How many miles do you drive each year on average? Usually you want to get to that break even point within 2 years.

[powerboatr]

Quote:

Originally Posted by Paw John Has anybody concedered changing out the front and rear diff. gear ratio on a F350 dually from 3:10 ratio to 3:73 ratio. I owned a 2001 F250 with 3:73 ratio and was making 18 MPG on the Hwy and 16MPH pulling my 36ft Mobile Suite. I now own a 2002 F350 4x4 dually with 3:10 gears and not getting good fuel mileage. It's getting around 12.5 mpg pulling my camper, 15 mpg in town driving and about 16 mpg on the high way. I was just thinking that if the cost of the ratio change is worth the future MPG savings. I'm thinking the cost would run about $ 1000.00 per diff. and I could do the work myself.

you sure its not a 4.10 in the dually? ford didnt put 3.10 in a dually 350.
my 6.0 with 4.30 gears gave us 12-13 pulling the 40 foot fiver.
it was a dually crew cab 2006 vintage
my 02 dually with 4.10 gears and the 7.3 never got above 11 pulling and 16 empty

[Paw John]

Powerboats

You are right, I'm sorry I have 4:10 ratio rear ends in my F350. As of now I'm still working and have about seven to ten years to go until retirement. I'm currently driving about 7500 to 8500 miles a year, I was thinking that if I do it while I'm still working and spead the cost over a couple of years. Like buy the front diff. parts the first year and then the rear parts the next year. Then do the install after that. I will also install 5 inch exaust system with exhaust brake (eather before the gears are after). Then my truck will be ready for the fulltiming road. I'm thinking that if I spread the up grade cost over seven to ten years will help the hurt in the pocket book.

[powerboatr]

also if you drop to a 3.73 then the tow capacity goes down.
cost savings running empty may be considered but the best thing is to slow down
the 7.3 can be trimmed with a programer and better flowing exhaust


mine i ran a 40 hp tune for towing and added a 4" free flow exhaust with muffler
it gave me 1-2 mpg gain empty
but also lowered the exhuast temps over 300F


imo 7-10 years the engine will be due an overhaul.
save the $ and get a gass sipper to drive to work if possible

[wingnut60]

Put in a GearVendors overdrive--cost will be close to changing gears on both differentials. Also check out USGear for same type change.
Joe

[Paw John]

Wingnut60


I checked out the web site of Gear Vendors / overdrives. That is a very good product from all that I read. Has any body installed it on their truck and how did it perform. How about you Wingnut60 do you have it are how did you come accross it. I'm very interested in this system and due to the easy installation it would be a quicker install and probable better fuel mileage. I would like to hear any pro's and con's on this system. Thanks for the input.

[wingnut60]

I don't have one, but thought seriously about it on an '04 350 I had, because I was driving over 70000 miles/year. Never quite got it done. I think the only downside on them is a limitation of how much towing load you can expose them to, and the torque of the newer trucks.
I don't think much of the gear ratio changes--too much chance to end up with a gear whine if the gear clearances aren't perfect.
Overall, if you don't drive over 100000 miles, there is no fuel cost payback, have seen several cost studies done couple years back.
You are much better off staying as is, the possible fuel savings either way between a 4.10/3.73 (9%) and a GV at 22% (cost $3400+) will never see a return.
Joe

[aspeyrer]

How can that be true? I thought the 4;30 REAR GEAR WOULD GIVE YOU LESS FUEL MILEAGE. I to have a 2007 F 350 Dually with 6.0 turbo diesel with 4:10 rear gear and get 8 to 10 towing my 36 foot toy hauler fifth wheel. In town i get about 11 to 12, and 15 to 16mpg on the highway

Quote:

Originally Posted by powerboatr you sure its not a 4.10 in the dually? ford didnt put 3.10 in a dually 350. my 6.0 with 4.30 gears gave us 12-13 pulling the 40 foot fiver. it was a dually crew cab 2006 vintage my 02 dually with 4.10 gears and the 7.3 never got above 11 pulling and 16 empty