How your JLUR runs after migrating from 33" to 37"?

[CapitanBlack]

Re-gear newbie questions:
Recently added 3" ARB Old Man Emu lift - next stop is 37" tires... Do you like how's your JLUR running on highway after tires swap? Did you feel any torque/speed loss and more gearbox noise after the swap? Are you considering (or already done) re-gearing you JLUR after tires swap? What re-gear kit could you recommend? Thanks!

Sponsored

 

[PaPasJP]

The 37's do take away from the torque/speed but not as bad as I thought. I don't have any extra noise or problems with 37's.

I have decided not to do a gear swap as it drives nice, has good pickup and I see 8th gear a lot more than I thought I would.

Plus saves me money and warranty problems.

My 3 cents, adjusted for inflation..........

 

[Token]

Re-gear newbie questions:
Recently added 3" ARB Old Man Emu lift - next stop is 37" tires... Do you like how's your JLUR running on highway after tires swap? Did you feel any torque/speed loss and more gearbox noise after the swap? Are you considering (or already done) re-gearing you JLUR after tires swap? What re-gear kit could you recommend? Thanks!

Using basic math, you can figure out the gearing to use.

New tire size X existing gear ratio / old tire size will get you into the ballpark of running the way it did stock.

So 37*4.10/33= 4.5969

Closest commonly available is 4.56

Re-gear to 4.56, and of course reprogram for the new gears and tire size, and your Jeep will operate pretty much like it did stock.

The next step would be 4.88
This would give you the ability to crawl better, but you’d run higher rpms on the street, so you’d take an mpg hit there.

The 4.88 will also deal with the increased rolling resistance, and unsprung weight the bigger tires add.

All depends on what you use your Jeep for mostly.

In my case, for the wheeling I do, which is mostly trail rides, with some decent obstacles where rock is usually wet or mud covered, and requires a bit of momentum anyway, I don’t need the absolute lowest gears.

Even an all stock Rubi with the 4:1 transfer case and 4.10 gears is lower than I need.

 

[CapitanBlack]

Awesome answers, thank you guys!

 

[rustyshakelford]

We have two JLs on 37s. One auto one manual. Manual was regeared to 5.13s. Made it much better to drive. Honest 16-17 mpg consistent average. The auto is still on 4.10 gears and somehow we’re getting 18-19 every tank out of it. If you have a manual, they really need to be changed to regain decent driving characteristics. For the auto, the 8 speed compensates great and then it just comes down to personal preference I think

Brett

 

[Halstem1]

I'll echo Brett. It wasn't nearly as bad as I thought with the auto. I average 18-19 MPG. and the power feels very similar or better to the stock sahara JK that I traded. So I'm happy. LIkely won't re-gear unless I have a reason to open the axle. No reason to.

 

[Token]

Another important factor is whether you tow.

If you do any towing with your JL the regear is going to be necessary.

 

[LunchBoxFab]

We have two JLs on 37s. One auto one manual. Manual was regeared to 5.13s. Made it much better to drive. Honest 16-17 mpg consistent average. The auto is still on 4.10 gears and somehow we’re getting 18-19 every tank out of it. If you have a manual, they really need to be changed to regain decent driving characteristics. For the auto, the 8 speed compensates great and then it just comes down to personal preference I think

Brett

same. my 5.13s were a god send for the manual transmission and the 37s. it was such a dog with the 4.10s and 37s

 

[Zandcwhite]

Everyone wants to do the math to compare stock size tires and gear ratios, but ignore the fact that the rubicon is geared far lower than necessary. A stock sport with 3.45 gears and 31.5" tires has the equivalent drive ratio of a 36.5" tire with 4.10 gears. They don't have the 4-1 transfer case either. You'll have the equivalent drive ratio of a sport and a much better crawl ratio without having to spend thousands regearing. The lower the gears the weaker the pinion as well. Unless you're going 40's or bigger, no need to regear.

 

[HuckleMonster]

I just had my JULR regeared to 4.88. I don't think 4.56 is available for the Rubi, could be wrong. It wasn't offered and I didn't consider it.

My jeep ran fine with 4.10's but rarely hit 8th and would bounce down out of 7th occasionally. Of course it will matter how much lift you add, if you add heavy tires/wheels, bumpers etc. 4.88 is great for me. I'm in 8th at 80+. I have a feeling those who say they stuck with the 4.10's with 37's and are driving in 8th gear, aren't as heavy as I am (weight and foot).

As for the math; that helps to get close to the stock gear ratio, all else being equal. ie, no additional weight or lift. Something to think about.

Milage, I was getting 13.5 with 4.10's now i think I'm getting 14.5 mpg. Didn't think that would happen but I just had them installed and that could be wrong. You guys getting 17-18.... get out of the left lane, you're holding up traffic, FFS.

Of course, whether you need regearing or not is going to be completely different between each jeep and each driving style.

There it is... my .02.

Sponsored