Gear ratio

[Wsutherlin]

4.0, 32rh 3 speed auto, 31x10.50r15

From what I’ve read, 3:73s would be optimal for 31s. But would 4:10s be too much or is there any down side to going with 4:10s with 31s? I know 4:10s would be perfect for 33s and if I go to 33s it will be a few years down the road.

Thanks,

 

[machoheadgames]

If there’s any chance you’re going with 32-33” later, I’d do the 4.10s. The difference between each inch of tire is not drastic when overgeared, it’s just a bit extra. So 4.10s and 31’s won’t be bad to deal with even for a few years.

 

[bbaldwin237]

If there’s any chance you’re going with 32-33” later, I’d do the 4.10s. The difference between each inch of tire is not drastic when overgeared, it’s just a bit extra. So 4.10s and 31’s won’t be bad to deal with even for a few years.

I was in the process of typing the same. Second this. Decide on your final tire size first and build towards that.

 

[GoldenGorilla]

Gears are definitely a job you don't want to do twice. Jeep opted for 4.10 with the Rubicon which came stock with 31s. 4.56 is generally the gear for a manual with 33s. I ran the stock 4.10s with 33s in my TJ Rubicon for 20 years before changing to 4.56 over the winter. I feel there are pros and cons to both ratios at 33 with a manual, but definitely wouldn't want to be any taller than 4.10.

It is ultimately a personal decision and one of the best tools to help you figure out what would work for you is the grimm jeeper gear calculator.

 

[JMT]

Gears are definitely a job you don't want to do twice. Jeep opted for 4.10 with the Rubicon which came stock with 31s. 4.56 is generally the gear for a manual with 33s. I ran the stock 4.10s with 33s in my TJ Rubicon for 20 years before changing to 4.56 over the winter. I feel there are pros and cons to both ratios at 33 with a manual, but definitely wouldn't want to be any taller than 4.10.

It is ultimately a personal decision and one of the best tools to help you figure out what would work for you is the grimm jeeper gear calculator.

Uh, just because you have a manual doesn’t mean you need 4.56’s. What manual you have matters. Same with auto’s.

 

[TheBoogieman]

4.0, 32rh 3 speed auto, 31x10.50r15

From what I’ve read, 3:73s would be optimal for 31s. But would 4:10s be too much or is there any down side to going with 4:10s with 31s? I know 4:10s would be perfect for 33s and if I go to 33s it will be a few years down the road.

Thanks,

I ran 32s with 4.56 gears and a 32rh auto. Not the best choice for highway use but felt great in town and offroad. The difference between 3.73 and 4.10 isn't worth the money IMO unless you're just swapping in axles from a 4 cylinder Jeep. I did that on a Jeep I bought with 3.07 gearing.

 

[Ir0nH3@d]

4.0, 32rh 3 speed auto, 31x10.50r15

From what I’ve read, 3:73s would be optimal for 31s. But would 4:10s be too much or is there any down side to going with 4:10s with 31s? I know 4:10s would be perfect for 33s and if I go to 33s it will be a few years down the road.

Thanks,

4.10s and 31s with the 32RH is a little deep, but not terrible

65 mph = 2889 rpm
70 mph = 3111 rpm

for reference
3.73 and 31s with the 32RH
65 mph = 2628 rpm
70 mph = 2830 rpm

 

[GoldenGorilla]

Uh, just because you have a manual doesn’t mean you need 4.56’s. What manual you have matters. Same with auto’s.

Agreed and that's why I recommended the Grimm Jeeper gear calculator. It's a MUCH better resource than the crappy banded charts you see and ultimately IMO it's a personal decision and you shouldn't listen to people you don't know on what the "right" ratio is for you.

I don't like automatic transmissions generally so I tend to ignore them but am aware the ratios are different and have different needs. I also recognize that if I had a NSG370 instead of a NV3550 (or AX-15) I probably wouldn't have felt any need to change my gears.

I've posted in other places the specific reason that I did ultimately decide after over 20 years to put in the 4.56 with my tire size having to do with a specific place that I need to drive through at high altitude, high grade and high-ish speed limit with traffic that has become increasingly intense over that time. I've also been frank that I feel the higher ratio has downsides and that's something I don't think the always gears and only gears majority is up front about. I drove my TJ on stock 4.10s for a very long time.

 

[jjvw]

Gears are definitely a job you don't want to do twice. Jeep opted for 4.10 with the Rubicon which came stock with 31s. ...

To add, there is no way 4.10 pushing 31s was the appropriate gear for all three transmissions available for the Rubicon.

 

[jjvw]

Agreed and that's why I recommended the Grimm Jeeper gear calculator. It's a MUCH better resource than the crappy banded charts you see and ultimately IMO it's a personal decision and you shouldn't listen to people you don't know on what the "right" ratio is for you.

I don't like automatic transmissions generally so I tend to ignore them but am aware the ratios are different and have different needs. I also recognize that if I had a NSG370 instead of a NV3550 (or AX-15) I probably wouldn't have felt any need to change my gears.

I've posted in other places the specific reason that I did ultimately decide after over 20 years to put in the 4.56 with my tire size having to do with a specific place that I need to drive through at high altitude, high grade and high-ish speed limit with traffic that has become increasingly intense over that time. I've also been frank that I feel the higher ratio has downsides and that's something I don't think the always gears and only gears majority is up front about. I drove my TJ on stock 4.10s for a very long time.

It is far easier to focus on the final drive ratio of whatever transmission is in use.

 

[suicideking]

My 2006 had 4.56 and the 6 speed when I got it. 4.56 wasn't terrible for 35's, but 5.13 was ideal. I would think 4.56 would work well for 33's if you have the 6 speed.

Going from 3.73 to 4.10 - Not worth it unless you are getting parts for free and can do the work yourself. Definitely not worth paying for just one jump in gears, you won't notice enough of a difference.

 

[pbeach]

4.0, 32rh 3 speed auto, 31x10.50r15

From what I’ve read, 3:73s would be optimal for 31s. But would 4:10s be too much or is there any down side to going with 4:10s with 31s? I know 4:10s would be perfect for 33s and if I go to 33s it will be a few years down the road.

Thanks,

'06 TJ, 2.4L on 33s...

FWIW, I upgraded three years ago:

Yukon Gear & Axle Front & Rear Ring and Pinion kit - Dana 30 Front / Dana 35 Rear - 4.56 gear ratio (from 3.73)
Part # YGK005
www.yukongear.com/shop/ygk005

EATON 912A569 Trutrac Limited Slip Differential for 27 Spline Dana 35 Axle with 3.54
Part # 912A569
https://www.eaton.com/us/en-us/skuPage.912A569.html

Summary: the fun returned — a noticeable performance boost for the dinky 2.4L. Essentially, I'm one gear higher throughout the range — highway: used to be at 2400+- RPMs in 5th @, say, 55-60mph — I'm now comfortably cruising in 6th, 2400+- RPMs @ 65mph. Before, I often enough wouldn't see 6th on the highway because I never had the power to maintain, especially into the wind or uphill.

 

[mrblaine]

Gears are definitely a job you don't want to do twice. Jeep opted for 4.10 with the Rubicon which came stock with 31s. 4.56 is generally the gear for a manual with 33s. I ran the stock 4.10s with 33s in my TJ Rubicon for 20 years before changing to 4.56 over the winter. I feel there are pros and cons to both ratios at 33 with a manual, but definitely wouldn't want to be any taller than 4.10.

It is ultimately a personal decision and one of the best tools to help you figure out what would work for you is the grimm jeeper gear calculator.

Not that it matters but there is more than a fair bit of scuttlebutt pointing to the Rubi models being built around 33's from the factory and then shut down for reasons unknown but speculated about more than a bit. Mostly pointing to lawyers and bean counters teaming up against the design team. I know none of that to be fully accurate though but I've seen it enough that it explains the odd gearing.

 

[jjvw]

Not that it matters but there is more than a fair bit of scuttlebutt pointing to the Rubi models being built around 33's from the factory and then shut down for reasons unknown but speculated about more than a bit. Mostly pointing to lawyers and bean counters teaming up against the design team. I know none of that to be fully accurate though but I've seen it enough that it explains the odd gearing.

One often repeated story is that the 2003 Rubicon speedometer was never correct from the factory. Mine was not when i bought the Jeep and it only became accurate after I installed 33s.

 

[machoheadgames]

One often repeated story is that the 2003 Rubicon speedometer was never correct from the factory. Mine was not when i bought the Jeep and it only became accurate after I installed 33s.

In my experience, the speedo is never accurate from the factory, it is always fast by about 4-5 mph fast at highway speed. Which would align with yours becoming correct with 33's.

The odometer, however, has always been correct on the stock tires (once again, in my experience), and gets shorted miles with the larger tires that correct the speedo. I think that is just an intentional buffer to protect against larger tires and speeding.

I could see the design being built around 33's making sense, although I don't think the speedo points to it.

 

[Wsutherlin]

For the record, I believe I’m running the factory 3:07 still.

 

[jjvw]

In my experience, the speedo is never accurate from the factory, it is always fast by about 4-5 mph fast at highway speed. Which would align with yours becoming correct with 33's.

The odometer, however, has always been correct on the stock tires (once again, in my experience), and gets shorted miles with the larger tires that correct the speedo. I think that is just an intentional buffer to protect against larger tires and speeding.

I could see the design being built around 33's making sense, although I don't think the speedo points to it.

My experience with multiple vehicles I have compared to GPS show speeds about 1-2mph fast on the highway.

I don't know how to verify that the odometer is recording miles with a different calculation than what the speedometer is displaying. I would assume both are using the same math.

 

[machoheadgames]

My experience with multiple vehicles I have compared to GPS show speeds about 1-2mph fast on the highway.

I don't know how to verify that the odometer is recording miles with a different calculation than what the speedometer is displaying. I would assume both are using the same math.

Between Jeep, Nissan, and Toyota, all of mine have functioned about the same, where the stock tire size reports fast speed on the highway (Nissan and Toyota were 3 mph fast, Jeep was 5ish (TJ & YJ), and upsizing tires by 1-2" fixes the speedo.

The odometers were all accurate, which I figured out by using my GPS and starting a trip while sitting still, then driving 50 miles or so and the tracking was 100% accurate on all of them, in stock form. Add the larger tires and it slows down by about 3-4%, which the GPS racks up more miles than the dash.

I think what they do is make the odometer perfect, then build the speedo to add a bit of buffer above that. I've done the math on the speedo gear Jeeps and the gear teeth used with various ratios and tires, and all of them calculated out to accuracy for the actual tire sizes. There isn't any math I can do on a Rubi with the non adjustable sensor, because I can't measure what it puts out.

I did own a Ford that had an accurate odometer in stock form also, but the speedometer was only 1 mph high at highway speeds. Not surprising that Ford is different. Jeep had the most speedo error in my findings, probably because people upsize tires by a larger percentage than the others.

All this to say that I have found most offroad oriented vehicles leave some overhead for larger tires but they make the stock odometer accurate so they don't short you on warranty by 2,000-4,000 miles.

 

[bobbyo]

4.10s and 31s with the 32RH is a little deep, but not terrible

65 mph = 2889 rpm
70 mph = 3111 rpm

for reference
3.73 and 31s with the 32RH
65 mph = 2628 rpm
70 mph = 2830 rpm rpm

I'll add that my 31's with the 32RH are still running on the stock ratio, 3.07.

65 mph= 2250 rpm. Haven't checked 70mph but I feel the gearing is OK and no need to change.

 

[Cooper Smith]

I ran 32s with 4.56 gears and a 32rh auto. Not the best choice for highway use but felt great in town and offroad. The difference between 3.73 and 4.10 isn't worth the money IMO unless you're just swapping in axles from a 4 cylinder Jeep. I did that on a Jeep I bought with 3.07 gearing.

03-06 SE auto's have 4.56 axles too