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Anyone running 37's with 4.88 gears, 3.6L Pentastar and an Automatic

39K views 31 replies 20 participants last post by  Lab Lover 
#1 ·
Looking for feedback. I went with 4.88's due to the automatic and the gear charts that are republished every week on this site. I have ordered my 37's but I am now questioning if I need to jump to 5.13's or possibly 5.38's. Therefore I am looking for feedback from those running a similar setup.

BTW went with the Toyo Open Country R/T 37X13.5X17
 
#5 ·
I'm running 4.88 and 37x13.5r17 Cooper discoverer STT Pros with a 2013 JKU auto. It has plenty of power compared to when I had 3.21 and 35s. I used to have to use 4th gear if there were any slight slopes to keep the speed on the highway, but now I can still accelerate in 5th on those same slopes.
 
#10 ·
I have 38s and 4.88s and think it's perfect. Does great on road and off.
 
#11 ·
I run 37s with 5.13. That really allows you to crawl the 4:1 Offroad in Rubicon. If you are a mostly street and mild trails - 4.88 will be fine. It will be the equivalent of a stock 4.10 Rubicon on stock 32 inch tires, around 2500 rpm at 70. The 5.13 jump up to around 2700 rpm.

I am a 3.6 automatic (2014).
 
#12 ·
Great information! Thanks. I run 2950 RPM right now at 75mph with 35's. It sounds like a consensus that I need to move to 5.13's. Even though it is mostly street driven I am optimizing for trail performance.
 
#16 ·
I'm likely going with 4.88 when I move to 37s. If you use heavy tires like Nittos and Toyos, it will be smart to go 5.13. I'll be using MTRs, KO2s, or something relatively light.
 
#17 ·
To complicate matters I am going with the 37X13.50X17 Toyo Open Country R/T - which is D range not E and weighs 10lbs. less per tire than the Toyo M/T and 10 lbs. more than the KM2 37". It is the hybrid between an AT and the MT. I like the fact that it was lighter, load range D (hoping for a smoother ride) as well.
 
#18 ·
Those 37s probably measure 36? KO2 37s are around 35.5...5.13 in that case would be too much. I'd probably do 4.88s but I do not want deeper gearing that the stock 31/32s tire had with 4.10s. It would be a bit tiresome on the highways and long drives. Most here do 4.88 with 37s and we have altitude which can suck power. The shops here recommend 4.88s too. The lead tech at my Jeep dealership is a Jeeper and recommends the same. So for me, 4.88s will be it. Maybe call some reputable Jeep shops and ask them what they think.

The Toyo you're using would be the only Toyo I'd consider, in the hope it will be a softer ride and I bet it will be.
 
#19 ·
I run 37's cooper stt pro mud terrains, Metalcloak bumpers with a 37 inch tire on the back carrier, steel wheels, full rock hard skids, a warm 10k winch, steel front poison Spyder fenders, poison Spyder steel rocker knockers, back aluminum poison spider fenders, stt pros measure 36.25. My gears are 4.88, I use my jeep both on and offroad. Plenty of acceleration, slightly more kick to them then stock. I've never come across an obstacle I would want 5.13 over 4.88. No need for more off the line acceleration in a jeep. My buddy has 5.13 and I've driven his jeep offroad, 5.13 is fine for offroad and on as well although rpms are higher. You could expect more kick upon pedal push with 5.13's which IMO is harder to control on large obstacles. Go with 4.88 and call it a day.


Sent from my iPad using Tapatalk
 
#22 ·
Just went down this road



Sounds like you are following me down the rabbit hole.

2016 JKUR Auto
37's / 4.88's

A few things for you to consider on this:

1. The guy who did my gears stated that if you go up to 5.13's that the gears are approximately 30% weaker than the 4.88's
2. There is conflicting information on this, but make sure you find someone who clarifies it for you as to whether 5.13's will even fit inside your D44
3. My rig is decent on the freeway when running flat, but when we head over any incline of substance - it's a chore to get up the hill. I'm of the opinion that no amount of gearing is going to fix this, it's a simple matter of weight vs. HP, and mine doesn't have enough HP anymore.

I anticipate that you will get many opinions on this, and not a lot of them will line up (as shown in what you've gotten already).

#YMMV

Good luck!
 
#26 ·
I've got a 2012, JKU, Rubicon, auto trans. Currently has 4:10. I've recently gone to 37's and done a bunch of upgrades to accommodate them. I'm at the gearing point now and can't decide between 4:88 or 5:13.
I'm running 37 MTR'S and they have measured a true 37. Shocking, but we've measured them a few times. My wheels are an OMF beadlock and are heavy. I'm going to say it's 70% street driven 30% offroad. I live 300 miles from the trails we do the most. So I'm highway driving to our home there and back.
We have 5:13 in our TJ on 37's. But it has an atlas and is 95% trail rig. I cant really compare to it. I really don't want to make the wrong choice, it's not like a bumper I can just swap out.
Thanks,
Lisa
 
#30 ·
I was told it will hunt gears on big hills, have you driven up many grades and noticed that?
Thank you.
 
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