Gear Ratio for 37s

[OL Sarge]

i have 30 in front and 44 in rear

 

[Mike_JK_Houston_711]

We've got 5.38's in our 3.8L and 5.13's in our 3.6L. Both JKUs on 37" Cooper STT Pros. Happy with both set ups, though the 3.8 is definitely slower. Here are charts for both the 3.8 and the 3.6 that might help.

View attachment 207653
View attachment 207652

Love this chart. Love me some Blue action!

 

[pbujk13]

Wait...what axle are you running? If it's a D30 the 5:13 pinion will be awfully small. On a D44 you'll be ok

^
I would consider staying conservative at 4.88 and risk some sluggishness in a D30.
I was warned all day about this by everyone from mall crawlers to mechanics when I got my D30 re-geared.
At 5.13 things get too small and starts making people nervous.
I am not going to a true size 37 ( possibly upgrading from my 315/70s to some true 35-36 range tires ) so I stuck with 4.56 since I would be fine based on the charts and ended up with an elocker - 4.56 btw is awesome on my 315/70 "35s".

Oh and gussets, sleeve/truss, and new balljoints possibly axle shafts. consider the tierod/draglink upgrades too if you are still on stock....

 

[Brute]

I have a PR60 rear with 4.88, 37" Toyo OC MT's and a 5.7 hemi, 5spd auto NAG1...I'm at 2600 rpm at 70 mph

Check out Novak Conversions gearing page https://www.novak-adapt.com/knowledge/gearing/