Why gear to run?

DBrown21 · Sep 30, 2012

I am getting 37x12.50r16.5 military tires soon, but with my 3.7L v6 dodge ram people have advised me to run a different gear ratio. Which gear should I run, 4:56 or 4:88 or any other ideas? How much change in gas mileage should I expect?

swamp_life hemi 05 · Sep 30, 2012

4.88's and its gonna go down substantially.....

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Hemi450hp · Sep 30, 2012

Are you going to shave your calipers to clear those 16.5" wheels? Smallest you can fit over the factory calipers are 17". And yes, you are going to want 4.56's at least. That is a huge tire for an underpowered engine.

4x4Hemi · Sep 30, 2012

I think you might be switching over to the Gallons per Mile range with that one

Catchin Zs · Sep 30, 2012

4x4Hemi said:
I think you might be switching over to the Gallons per Mile range with that one

X2, maybe. Some off road beaters run 40's on 1.3L Samurai's. But with 5.29 gears

D33k · Sep 30, 2012

What are military tires? 4.56 is a good match for 37s but I'm afraid you may be under powered.

05singlecabHEMI · Sep 30, 2012

Hemi450hp said:
Are you going to shave your calipers to clear those 16.5" wheels? Smallest you can fit over the factory calipers are 17". And yes, you are going to want 4.56's at least. That is a huge tire for an underpowered engine.

what he said on the wheels. need to shave down the brake caliper down.

also with 37 military tires on a 3.7 even with gears your mpg is gonna sink low. gears will help a bit. my buddy had a silverado with the 5.3L or 5.2 cant remember which is chevy, had it on 37s and he was getting about 7mpg without gears. so youll probably expect 5-10mpg even with gears i bet. could be wrong, its just gonna put a lot of strain on your motor.

DBrown21 · Sep 30, 2012

Ughhhhh. I knew I should've gotten at least the 4.8L..... But if ran a 33 or 35 tire would I need a different gear and not murder my gas mileage?

D33k · Sep 30, 2012

DBrown21 said:
Ughhhhh. I knew I should've gotten at least the 4.8L..... But if ran a 33 or 35 tire would I need a different gear and not murder my gas mileage?

They are lighter so yes better off, what are your stock gears?

swamp_life hemi 05 · Sep 30, 2012

If I were you I would do 35's on 17" rims, and do 4.56 gears. Your mileage wouldn't be too bad.....

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DBrown21 · Sep 30, 2012

Im not sure on what is stock. I found a 33x12.50x16.5 I shouldn't have to change gears for that?

D33k · Sep 30, 2012

DBrown21 said:
Im not sure on what is stock. I found a 33x12.50x16.5 I shouldn't have to change gears for that?

Call your dealership give them the vin, you can find the size, it really depends on what your looking at stock. My hemi has 3.55s and with 35s is sluggish.

TheSatinPumpkin · Sep 30, 2012

Prob not but still be a barge to get up to speed.

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KGBIGCOUNTRY · Oct 1, 2012

That thing is gonna be zinging on the interstates

Hemi450hp · Oct 1, 2012

You are still going to have to address your calipers for that 16.5" wheel. It will not fit over your calipers without taking a grinder to them. I know you can find these wheels/tires cheap, but shaving calipers is a pain.

DBrown21 · Oct 1, 2012

Yeah grinding calipers are the least of my worry now. They're cheap that's the only reason i was really leaning that way. I don't need a good off road gear, just something to move the tires without too much of a drop in gas mileage. I can handle a few mpg less but not in the 5-10 range. I mean idk If its even possible, but someone mentioned maybe a smaller gear. I just need to know what todo

NWRQC · Oct 2, 2012

DBrown21 said:
Yeah grinding calipers are the least of my worry now. They're cheap that's the only reason i was really leaning that way. I don't need a good off road gear, just something to move the tires without too much of a drop in gas mileage. I can handle a few mpg less but not in the 5-10 range. I mean idk If its even possible, but someone mentioned maybe a smaller gear. I just need to know what todo

Calipers are cheap, but they are not a part that I would want failing on me.
Like others have said, the 3.7 is already under powered for the truck so even with the 4:56 gears you will probably see a substantial drop in fuel economy.
I think the 3.7 is rated for about 14 city and 18 highway (or close)..I wouldn't be surprised if you were getting 9-10mpg city and 11-12mpg highway after the gear swap. 37's are heavy and thats a lot of unsprung weight for the 3.7 to move. My buddy has a RC 3.7 manual with 285/60/20's (33.4" tire) and even that felt like a dog. I didn't like driving his truck, and I cant even begin to imagine how gutless it would be with 37's.

SmokedRam · Oct 2, 2012

If you had a 3/4 or one ton truck, you could run the military Hummer 16.5 steelies without modding the calipers.

DBrown21 · Oct 2, 2012

On the rear end it says 3.92 open case. But a friend said 4.10 gear would be good. If I could find a decently priced 35 tire I'd get it but I just can't find any anywhere. I looked on how close my calipers are now and it's about a 1/2 or so so I'll just have to see. What has mileage should I expect with a 4.10 gear?

Why gear to run?

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