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Regear for 37-35 inch tires

20K views 21 replies 13 participants last post by  inksterJK 
#1 ·
What is the optimal gear ratio for 35-37 inch tires?
 
#7 · (Edited)
A 3.8, with a 6 speed manual, should run for optimum, a 5:13..........:thumb:
 
#8 ·
I got a 2011 auto with 35's that I just regeared to 4.88 3 weeks ago and Ive already taken it up into the mountains here in Colorado and it's perfect. It seems to have plenty of juice and no more engine screaming like before.
 
#11 · (Edited)
^^^3.8, with a 6 speed manual, then should run for optimum.....4:88.:thumb:

But strictly as a DD, flat area, with little to no off road usage, then for your type of driving, a 4:56 maybe better suited for you!
 
#13 ·
Depends, what engine/tranny?
And where you live and how you plan on using your jeep.
Probably the single most crucial mod, mechanically, you'll do to your Jeep.

Gearing is sooooo subjective. Heed the posts above.

Things you need to consider: terrain of common driving (mountains vs flatlands), tire size, whether you drive a manual or an automatic...it really is one of the most frustrating, expensive decisions you'll make about your Wrangler. And the one that, if you get it wrong, can make your Jeep life absolutely suck.

Now that I've scared you, here's a link that deals with gearing for the Pentastar engine.

This one starts out dealing with the pre-Pentastar engine, but then goes on to deal with the issue as a whole. Several valuable charts in here. Most of them deal with the problem of running 35" tires, but if you extrapolate, you'll see the relationship to running 33s, towing, etc. Read closely... Want 35s dont want to REGEAR ??

If you decide to do a regear, some advice:

1. If you have a manual transmission, aim low. Better to have to downshift than have a Jeep that screams (rpm-wise) in high gear on flat roads.

2. Find a shop that's proficient on regearing (preferably on Wranglers). Buy the master kit (gear sets, install kit, carriers) from them to ensure warranty coverage. Otherwise, they can blame the mfr, etc, if things fail. Make sure they order extra pinion bearings and crush sleeves, which have a tendency to get trashed during removal / install.

3. Follow the post-install instructions to a T. You should be limited in how you drive your Jeep, vis-a-vis rpms, for about 500 miles or so. Just like breaking in a new engine. A competent gear mechanic should give you a fairly rigid schedule of driving, gear oil change, inspection instructions, etc.

Depending on where you live, a gear change, regardless of ratio, will cost you ~ $1200-$2500.

Anyway, all food for thought. Good luck with it...
 
#14 ·
This one starts out dealing with the pre-Pentastar engine, but then goes on to deal with the issue as a whole. Several valuable charts in here. Most of them deal with the problem of running 35" tires, but if you extrapolate, you'll see the relationship to running 33s, towing, etc. Read closely... Want 35s dont want to REGEAR ??

If you decide to do a regear, some advice:

1. If you have a manual transmission, aim low. Better to have to downshift than have a Jeep that screams (rpm-wise) in high gear on flat roads.
Kbw
What do you mean by aim low?

I'm currently considering either 4.10 or 4.56 for my 3.8 manual. I was reading the thread you linked and with 33s based on 2500rpms at 70, 4.10 would be right on the mark. If I were to go with 35s then id need 4.56 to be around 2600

Of course my jeep is mainly stock atm but I do plan to add a front bumper and winch in the future.
 
#15 ·
I have a 2014 JKU, 3.6L, 6 speed manual, 33" tires. I just ordered 4.56 gears and the master install kits for both. I do take it off road, mud, and some rocks. It also sees the highway occasionally for family visits, etc. I'll also be ordering a detroit truetrac for the rear and a new carrier for the front - and even considering an Aussie lunch box locker for the front as well.

I *may*, in the future, consider going to 35's, but for now, 33's it is. Should I reconsider 4.10 gears instead of 4.56?
 
#16 ·
try it stock and see what you think. I have 37s with the 6-speed and its not too bad. Not bad enough for me to worry about changing gears. You'll pretty much lose 6th gear on the highway unless youre going 75+ but other than that, no big deal. With the 4:1 transfer case you'll still be geared low enough for most crawling.
If i were to change it would be to 5.13. I wouldnt go any higher than that as the pinion starts getting crazy small (weak).
Location depends a lot. I'd suggest just trying it out first and seeing if, or how much, you need to change.
 
#21 ·
^^^With the 3.6 and 37's a 4.88!!!!!!!!
 
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