Preparation for 37's

idpagal

New member
Hi all,

My husband and I are thinking of changing to 37 inch tires on our 2019 JLU Sport. Before doing so, I want to hear you guys opinions on what needs to be prepared, of course in addition to the tires. :D

Here is the list of items I have collected so far.
(1) Re-gear the differential. We plan to do so by either replacing our JLUS stock axles with JLUR axles (Dana 44s with e-lockers, 4.10 gear ratio), or upgrading the front axle to Dynatrac PR44 with a e-locker and regear both differentials to 4.88. (see my post on axle upgrade)
(2) 4-4.5 inch lift. Right now we are on 3.25 inch lift. Do 37s really need 4 inch lift?
(3) Control arms. Do we need to replace 4 control arms or there is a priority based on budget?
(4) Bump stops to limit the uptravel of 37s
(5) Adjustable track bars. We got front and rear adjustable track bars from Rancho. We can re-center the axle if higher lift is needed.

Thanks a lot in advance!
 

JP223/3USA

Member
Yes to the bump stops. They’re always a must and that’s why lift kits come with them. Personally, I would run at least front lower and rear upper control arms.
You could also add Rubicon fenders for more tire clearance and not worry about raising your center of gravity. Rubi fenders sit around 2” higher then the sport fenders


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Cozdude

Guy with a Red 2-Door
I’m about to run 37’s on my sport but I’m going with a rancho 2” lift and adding rubi fenders. At 3.25 you will be fine and not have to go higher.

You might need more bump stop for the 37’s but you can cycle your suspension once they are on and see how bad to rub flexed out.

For control arms front lowers will help adjust your caster even now for better handling and rear upper arms will be needed if you have aftermarket driveshaft.
 

Last edited:

klastinger

Member
Wanting to go to 37’s on my 2020 Rubicon. Have a 1.5 inch lift now, but thinking of going to 2” inch or 3” synergy springs. Already have all Synergy steering components and rear track bar. Have Rubicon Express adjustable control arms.

Suggestions on 2 inch or 3 inch springs?

Also looking at my gearing and looking at 4.56 or 4.88. Any suggestions?


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Cozdude

Guy with a Red 2-Door
Wanting to go to 37’s on my 2020 Rubicon. Have a 1.5 inch lift now, but thinking of going to 2” inch or 3” synergy springs. Already have all Synergy steering components and rear track bar. Have Rubicon Express adjustable control arms.

Suggestions on 2 inch or 3 inch springs?

Also looking at my gearing and looking at 4.56 or 4.88. Any suggestions?


Sent from my iPad using Tapatalk Pro

Here is my 2” rancho kit on my 20 sport. Sits perfectly. With a Rubi you will have plenty of room.

IMG_0738.jpg

I suggest synergy steering upgrades for sure.

For gears I think 4.88 is a good choice. Will give you plenty of gear to get 8th back when on the highway
 

idpagal

New member
Hi all,

Recent updates, we have upgraded to Rubicon axles on our 2019 JLU Sport. With 37 mud tires, 4.10 gear ratio feels sluggish. We plan to re-gear to 5.13 for more torque when go rock crawling. Any recommendations on re-gear kit? Revolution gear kit seems out of stock. The custom shop does not recommend Yukon gear kit. Did anyone use Nitro gear kit before? The good, the bad, the ugly? Any feedbacks are welcome.
 

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