Dodge gear changing/milage

[Ryan_V]

I have an 08 3/4 ton dodge diesel. It came with 4.10 gears. Is it possible to switch to say 3.73's? If so, how much would it cost, and what would I see for a milage difference? I dont believe I need those gears, and am just throwing it out there for a few more mpg's. Also, would this do anything for the warranty?

[Macgyver55]

My guess is it would run you around 1000 or so. (per axle if 4wd). Not sure about the warranty on the rest of the vehicle but it surely would affect the differential warranty, unless the dealer did the install where it may cost more.

Payback is determined on your current mpg as opposed to what you get for new mpg.

Say you get 19 mpg now and drive 15000 miles a year. Thats 789 gallons at average $4 per gallon = $3157

So if you get 20mpg after the gear change you will use 750 gallons at average $4 per gallon = $3000

Or, if you get 21mpg after the gear change you will use 714 gallons at average $4 per gallon = $ 2857

At 20 mpg you'll save $150 a year but need 6+ years to payback and up to 12 years if its 4wd.

At 21 mpg you'll save $300 a year but need 3+ years to payback and up to 6+ years if its 4wd.

Neither of those options would be worth it to me, but thats just me. I would opt for another more cost effective option. That would be to check for available tire sizes that fit the vehicle that are taller than what you currently have and will essentially give you a higher final ratio (similar to changing a gear size). It may not give you the identical outcome as the gear, but close to it. Tires are something you need or will need at some point and there is no guarantee that the gear change will net you the results you hope for. Tires would at least give you a good idea if it would improve mileage or not, and the ability to "go back" to the original size if it doesn't. For the cost of the gear change you could buy an additional set of tires on rims and switch them out based on the use of the truck. Stock ones for heavy pulling and taller road tires for general driving and mileage. If they dont work out as hoped, you can sell them and be out far less than a gear change would.

[Valv]

Ryan, I agree with Mcgiver 100%. You have a 4x4, you will need to replace both axles gears.

It is not a feasible solution unless you travel many miles/year.

Tire size would be the only viable option.

[Ryan_V]

Thanks guys for the information! I appreciate it. In the summer, empty, topper off, 55, cruise set, I pull around 20 mpg. Drops quite a bit in the winter. Just would like too do better, but average less than 5k/year, so totally not feasable. Thanks again. Good to have a place to get good info!

[delcecchi]

Cheapest way might be to find new differentials in a salvage place. Although this truck is pretty new for the parts to be available.

[311Hemi]

Throw some 35's on there and I would think that would help. It helped me run higher speeds at under 2000 rpms on my Dodge.

[Powerstroke]

Throw some 35's on there and I would think that would help. It helped me run higher speeds at under 2000 rpms on my Dodge.

Except now you've got a heavier tire with higher rolling resistance and possibly less aerodynamic if you have to add a lift to fit those tires. It won't work out.

Unless you recalibrated your speedo for the larger tires you're probably not getting any better mileage. Larger tires will make the odometer turn slower unless you have everything recalibrated.

I love putting 35's on my trucks, but I've never gotten better mileage afterwards.

[Valv]

Mileage in wintertime sucks for everything, even gas cars. Check it back in the spring, you will smile more.

[clownshack]

I would think you can get a bigger increase in fuel economy by installing a tuner. I have always had them on my diesel trucks and see 2-5 mpg increase.

[Powerstroke]

I would have to agree with clownshack. If you haven't looked into any performance mods for your truck, there are MPG's to be found in the motor with some programming changes. These diesel trucks are so detuned in order to comply with emissions standards its ridiculous. A programming change will get you a couple MPG's and more power without having to change anything else.

[Macgyver55]

I agree that tuners can also be a good viable option if used for the intended purpose of gaining mileage. More often than not though they are marketed for performance gains which they can deliver. They often require other expensive modifications like exhaust and intake to get the full benefits of their advertised gains. Where the problem comes in, (and I know first hand) is that if you like power and try it out you often offset any mileage gain by "playing" with the newly found power too often.

Also, based on his question about warranty I would caution that tuners can often void warranty.

[Valv]

Ryan, are you sure you have a 410 ? 20mpg seems too good for a short ratio.

[Ryan_V]

Thats what the window sticker says. I average much lower than that. Thats only cruising on the highway, resetting the overhead computer. It does have cold air intake and aftermarket exhaust.

[Valv]

The overhead computer is not accurate, best way to know for sure is to fill up, drive until empty, then fill up again.

As we said, wintertime mileage is the worse you can have, blended fuel, warmup time, cold and stiff running gear. All these add up to a very bad mpg rating.

[Ryan_V]

Yeah, I just use it to get an approximate idea! I know about how far off it is based on my fill ups!

[311Hemi]

Except now you've got a heavier tire with higher rolling resistance and possibly less aerodynamic if you have to add a lift to fit those tires. It won't work out.

Unless you recalibrated your speedo for the larger tires you're probably not getting any better mileage. Larger tires will make the odometer turn slower unless you have everything recalibrated.

I love putting 35's on my trucks, but I've never gotten better mileage afterwards.

Yep, I am aware of that and my speedo was recalibrated for the 35" (315's) tires...I had to walk the Dodge tech through it. While they are a heavier tire I don't know that the additional rolling resistance makes that much of a difference with a diesel. Granted, I never drove the truck with the 245 pizza cutters that were on there. I would have to images that the RPM different between the 245 and 315's cruising at 70mph would help.

How much resistance do the 35" tires really add? As much as pulling a small 16' boat? Can't say I really saw a drop in mileage with either behind the Dodge. 18-19 mpg on freeway doing 65-70 mph, 16-17 in the city with the 35's.

[PurpleFloyd]

I have the same truck and get the same mileage. I would look at a tuner if you want better mileage and if you are not concerned about the warranty I would look into the DPF delete also as it will give you more power and better mileage as well as getting rid of the soot buildup.

[Macgyver55]

.... if you are not concerned about the warranty I would look into the DPF delete also as it will give you more power and better mileage as well as getting rid of the soot buildup.

I wouldn't recommend it, just an FYI, these kits are intended for off-road use only, and installing them for use with on-highway diesels is illegal.

Found this on the first web site I looked at.

DPF Delete tuning products are STRICTLY FOR OFF-ROAD USE ONLY. According to the EPA Clean Air Act, they are illegal for use on any Federal, State, or Local public highways and illegal use is punishable by the penalties enacted by the mentioned laws. We do not condone illegal use of these products, and an Environmental and Liability waiver must be signed in order to purchase any DPF Delete products.

[PurpleFloyd]

So is driving faster than the speed limit, pulling a cargo trailer over 10,000 without a DOT etc.

It's not something I did or will do but some people find it to be a worthwhile mod.

[Macgyver55]

So is driving faster than the speed limit, pulling a cargo trailer over 10,000 without a DOT etc.

It's not something I did or will do but some people find it to be a worthwhile mod.

True, but neither of those carry a $2500 fine that many people don't realize until its too late.

[Valv]

True, but neither of those carry a $2500 fine that many people don't realize until its too late.

I thought it was up to $ 10,000 fine.

In any case, whatever you want to do with your vehicle is your (our) choice. As a public web forum we do not and cannot condone or encourage any illegal activity, I hope you understand that.

[shizzy]

Keeping my speed down has had the greatest effect on MPG. Staying between 55-60MPH on the interstate is worth 1-3 MPG over going 60-65MPG.

[delcecchi]

Keeping my speed down has had the greatest effect on MPG. Staying between 55-60MPH on the interstate is worth 1-3 MPG over going 60-65MPG.

Going 55 on the interstate strikes me as dangerous, as well as inconsiderate.

[Dozer]

Keeping my speed down has had the greatest effect on MPG. Staying between 55-60MPH on the interstate is worth 1-3 MPG over going 60-65MPG.

55-60 on the interstate? My time is way more valuable than that! Ive done the math, it comes to like $2.15 an hour. I dont do much for $2.15 an hour.