4.10 Gears and mpg

[Jkm412]

My truck has 4.10 gears and my tires are 285/75/16 would I gain MPG by getting slightly larger tires than what I have now?

[2003kingranch]

i gained almost 1mpg with 285's with 3:73's. should help with 4:10's also. help get the rpm's down

[Jkm412]

any more comments on my question?

[350factor]

I run 3.73 gears(says the id tag on axle) @ 325/65 R18 ~34" tires. When I'm at 2000rpm i'm going ~73mph. So I would agree with 'KINGRANCH'. I bet your running a bit higher rpm with the smaller tires and the 4.10 gears so in turn you should gain some by going a bit bigger. As to how much bigger before you start losing? I don't know. What are you running at your 2000rpm?

[tfifeco]

I have kind of a reverse question. I just went with 35" tires but running 3:73s - Would i Lose MPG noticably by changing gears to 4:10s? Just trying to figure out if its worth the expense to change. I know this really comes down to preference and either gear will work fine, but was just wondering if someone else has changed gears to 4:10s and can say whether it was worth it to them or not.

[350factor]

TFIFCO- From my experience of new ring and pinions and master install kits and then having someone else doing them it gets expensive for just one axle. you may spend up to $1500 just for both axles. If you have 35" tires and I have 34" tires and going lower to 4.10 may not be worth it unless your going larger tires than what you have already. Now this is obviously all assumption, but I'm very used to working on Jeeps and don't know the tire sizes well with these trucks. My jeep doesn't have these monster diesels and much beefier axles stock. So in return these trucks can handle quite a bit with out much mod'ing. So maybe someone with knowledge before i can research more can answer how big of tires can you go until your seeing significant mpg loss and need to re-gear. But I'd like to be fair and try to hear from JKM412 to solve his problem before we hijack the crud out of this thread.

[tfifeco]

Hey 350factor, true I don't want to hijack this thread, LOL - thanks for your input, btw, I have 2wd so it will be single axle and after more research, IF I change i think I will go with 4:56s rather than 4:10s ... Just not enough difference to warrant change. And I will probably do myself with my brother, he's done several jeeps as well and has all the tools.

To the OP, sorry Not trying to hijack your thread. And from what i found out after researching 4:10s and 3;73s are not much different so maybe negligable mph difference.

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[350factor]

I say unless the OP doesn't have any feed back we hijacked the thread like dirty pirates

[Jim@StreetLethalPerfrmnce]

i have about the same size on my dually with 4.10's...and at 65mph im at roughly 2100....i hate my 4.10's. larger tires would be better, but i have 285/75/17 or whatever size is one size up from stock. would like to change to 3.73, but time you buy 2 gear sets and 2 install kits and fluid, it will take a loonnnggg time to recover your money from fuel savings.

[Jkm412]

Originally Posted by 350factor

I run 3.73 gears(says the id tag on axle) @ 325/65 R18 ~34" tires. When I'm at 2000rpm i'm going ~73mph. So I would agree with 'KINGRANCH'. I bet your running a bit higher rpm with the smaller tires and the 4.10 gears so in turn you should gain some by going a bit bigger. As to how much bigger before you start losing? I don't know. What are you running at your 2000rpm?

My speedo shows 70mph at 2000rpm but it is slightly off since I am running a little larger than stock tires