JK Rubicon Axle & 37" Tire Question

**ruby red** · 04-22-2009, 09:41 PM

I have a ’07 JK Rubicon, 2 door. I lifted it with 3” Full Traction Ultimate Lift, Superior 4.88 gears, Tom Wood front & rear driveshafts and 35” Goodyear MT/R. I want to change to 37” tires to try to correct my RPMs that are running too high. My concern was clearance in the wheel well. A friend has a ’97 TJ and admits to knowing little about the newer jeep and since I only wanted an opinion on wheel clearance, I asked him for his opinion. He has not yet looked at the jeep, but this is what he told me in an email.
"What few people understand is that the parts on a Dana 30 that fail/have accelerated wear rates with 37" or larger tires are the exact (!) same parts that are used on a front Rubicon Dana 44 axle. The Rubicon's front Dana 44 uses the exact same axle tubes, u-joints, knuckles, ball joints, inner-C's, outer-C's, and outer axle stub shaft as a Dana 30. And it is those parts that aren't up to 37" or larger tires. The only parts that are different between a Rubicon front Dana 44 and TJ Dana 30 are the ring & pinion gears, center pumpkin (D44 housing), and inner axle shaft. Everything else is the exact same thing as a Dana 30.” Is this correct? I thought the JK had “beefier” axles than the TJ.

s1edneck700 · 04-22-2009, 09:47 PM

rpms too high? i hear 4.88 is spot on for a manual and 35's. most auto owners opt for 5.13's with a 35" tire....what are you spinning at 65mph?

**ruby red** · 04-22-2009, 10:01 PM

Close to 3000 rpms. I did some research and close to factory would be 4.88 with 38" tires. 38" are more pricey and harder to find, so I was looking at 37".

http://www.4wheelerssupply.com/jkbuildup/2006/11/

Warlord2 · 04-22-2009, 11:08 PM

Guess it depends on what you call factory. My X came with 29" tires and 4.10 gears, wich is close to 5.13's and 37"s.

I have that same lift and am not sure that 37's would fit without atleast adjusting bump stops. Mines very close to rubbing at full flex with just 35's and last time I was out the rear did have some very small rubbing a friend said. I think a 1" spacer or body lift would give clearance for 37's. Your friend is right about the axles. There has been some small problems running 37's but for $250 plus some welding they can be fixed. Many people are running 37"s without any problems.