Gears for 37" tires

[Renegade]

To what? (That's the point of this thread)

For 37s, and if money wasn’t a factor, I would probably do 4.88, in Dynatrac ProRock XD60s.

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[Southbayglad]

And I am of the opinion that 4.10 gears are the best if you have a Rubicon. Even if I didn’t have a Rubicon I wouldn’t go any lower that 4.30 on 37s.

DO you think that 4.30 would get it closer back to stock? I have to drive some major hills for about 2 hrs to get up to my cabin that I go to at least once a month. Do you think that Ill be fine? Im getting ready to throw 37's on and I have the 4.10's already. Im asking you since you have them. LOL

 

[TennesseePA]

My Gladiator will roll over 10k miles before I get home from work this evening. I have had 37s on it form most of those miles and I can say that the difference is imperceptible. I read all over the forum that going from 4.10 to 4.88 or 5.13 is only a couple hundred RPM so you won't notice the gas mileage difference and they are right. I am also right when I say that the additional 200-300 rpm makes almost no difference at all in horsepower and performance. I had a JK sport that came with the tiny little 29 inch tires and 2.73 gear. When I put the 35 inch destination MT tires on it I re-geared to 4.56 and it was too low for highway performance and I wish I had gone with 4.10 or 4.30 at the lowest. The new transmission is designed and programmed to keep the engine in its most efficient RPM range. Lugging an engine is not efficient at all so it will downshift to keep it back into its preferred range. i will reiterate that efficiency is defined as the least amount of energy expended to get the work done. The 3.6 is NOT a torque monster so lugging it will only add inefficiency. Don't take my word for it just throw your 37s on there and drive it for a few days and see for yourself. It's not like you can't re-gear it at a later time.

As far as hill go we have a few of those in Tennessee. I've towed my enclosed trailer all over Middle Tennessee, down to Florida twice and up to Gatlinburg and it does a great job. It just has to run high in the powerband because it is not a torque monster design.

 

[Southbayglad]

My Gladiator will roll over 10k miles before I get home from work this evening. I have had 37s on it form most of those miles and I can say that the difference is imperceptible. I read all over the forum that going from 4.10 to 4.88 or 5.13 is only a couple hundred RPM so you won't notice the gas mileage difference and they are right. I am also right when I say that the additional 200-300 rpm makes almost no difference at all in horsepower and performance. I had a JK sport that came with the tiny little 29 inch tires and 2.73 gear. When I put the 35 inch destination MT tires on it I re-geared to 4.56 and it was too low for highway performance and I wish I had gone with 4.10 or 4.30 at the lowest. The new transmission is designed and programmed to keep the engine in its most efficient RPM range. Lugging an engine is not efficient at all so it will downshift to keep it back into its preferred range. i will reiterate that efficiency is defined as the least amount of energy expended to get the work done. The 3.6 is NOT a torque monster so lugging it will only add inefficiency. Don't take my word for it just throw your 37s on there and drive it for a few days and see for yourself. It's not like you can't re-gear it at a later time.

As far as hill go we have a few of those in Tennessee. I've towed my enclosed trailer all over Middle Tennessee, down to Florida twice and up to Gatlinburg and it does a great job. It just has to run high in the powerband because it is not a torque monster design.

Thank you for the info.

 

[LeftCoast32]

Changing from 4.10 gears and 33" tires to 4.56 gears and 37" tires will keep the RPMs almost exactly the same when compared. This is my plan after the lift and tires. Right now I am keeping it stock for the installation and dyno time of the new TVS1900 Magnuson Supercharger kit. The supercharger will bump all the low end torque and increase the HP 100-120 over stock. The gear and tire change should be perfect at that point.

 

[JCJL]

4.88s here and it is perfect but hey what do I know LOL
Heading to Florida first week of December, post feedback soon

 

[KennyKustom]

I find my rubi hunts between 7/8 on 33's. My speed limit is 62mph. ( Canada) staying with 4.10 and 37, would knock that down to 5/6 gears.

 

[jrf]

I find my rubi hunts between 7/8 on 33's. My speed limit is 62mph. ( Canada) staying with 4.10 and 37, would knock that down to 5/6 gears.

Mine goes between 7/8 on the highway with 37s and the stock 4.10s. If it's a flat road it will stay in 8th, any type of grade it will drop. I live in a relatively flat area with small hills and very few steep inclines.

 

[smlobx]

I am certainly no gear expert but here is THE information you want...

 

[WhatExit?]

So, looking at the above chart:

Stock 33" tires on a Rubicon with 4.10 gears = 2426 RPMs

And, running 37" tires at 2426 RPMs puts the gears in the 4.88 box

 

[ShadowsPapa]

I know this isn't about the lowly Overland, but the manly Rubicon and massive tires, but I paid more attention today to mine - and with our hills, mine spends a lot of time in 6th gear when on roads with a 55 limit. It stays in 7th quite a bit otherwise, hits 8th only on more level roads. I don't see it in 8th for very long or very often unless I'm on a 65+ road with mild hills.
When driving the back roads home from DSM, it doesn't touch 8th gear much.
Made me wonder how it would do with any load since on a 55 limit road it was in 6th much of the time with the hills.
No way I could run larger tires on this thing!

 

[Oscar Indy]

 

[KennyKustom]

Mine goes between 7/8 on the highway with 37s and the stock 4.10s. If it's a flat road it will stay in 8th, any type of grade it will drop. I live in a relatively flat area with small hills and very few steep inclines.

But, what's your highway speed?

 

[WhatExit?]

Long video short: He says the Gladiator on 38’s needs a gear change. He went with 4.88’s after considering 4.56’s. For more info see my post above after the chart

 

[Oscar Indy]

Long video short: He says the Gladiator on 38’s needs a gear change. He went with 4.88’s after considering 4.56’s. For more info see my post above after the chart

You're the first to complain about that video but I guess that's the beauty of opinion.

That chart is BS tho all the numbers are completely wrong.

4.88 and 70mph on 37s will turn 2078 rpms
Same setup in 5.13 gears will turn 2185 at 70mph that chart is off by a LOT.

Try this instead.
http://www.grimmjeeper.com/gears.html
Your chart might be for a JK but it's clearly not for. JT or JL

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