What is needed to run 35’s vs 37’s

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Plumber1

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So being aTJ guys for yeas my buddy just bought a 2015 Rubicon Hard Rock edition. It is currently on 33’s but he would like to up size to 35’s or 37’s how much lift is needed and what else is needed such as gear, axels, steering ?

PS it’s an auto trans

thanks for your advise
 
Is it a DD or will it be doing offroading? If it's a DD the Jk should have 4.10's I believe, so he could get by without a gear change on 35's.

Will need to recalibrate the speedometer so the transmission will shift correctly.
 
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No it’s not a dd but not hardcore off road. It will do some trails like the Rubicon once a year and some others lighter trails a few time a year
 
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IMHO, for 35's on a Rubicon w/auto no re-gear is needed, but as Blackjku said, you'll want to re-cal the speedo to keep correct shift points etc. If I were to do 37's I would re-gear to at least 5.13.

For mild wheeling/trail riding on 35's I feel stock axle shafts and steering is sufficient, with that said, chromoly axle shafts are never a bad thing and you get a spare set out of your old ones. 37's, I would definitely go with chromoly's and take a hard look at steering components.

Lift. Lot's of personal preference here, I'm from the biggest size tire/least amount of lift school of thought. I'm running 35's on a 2.5" lift with flat fenders and have plenty of clearance, enough in fact that I could remove the lift and still clear. If I were to move to 37's I would be glad I have the lift, but with some strategic trimming, I could get by with no lift.
 
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Plumber1 said:
No it’s not a dd but not hardcore off road. It will do some trails like the Rubicon once a year and some others lighter trails a few time a year
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Good to see you over here…

These guys already got the gearing right. All that climbing up in the Sierras might be a consideration as well. I’m happy I got my 5.38s for my 37” tires. Although I need it with a weaker 3.8L. 5.13s and the 3.6L are a decent combo for 37s.

For a 2015 and some flat fenders: 2-2.5” lift for 35” tires. 4-5” lift for 37” tires.

As for upgrading the axles and components. A good driver and light on the gas stock axles should be okay with 35”. At 37” I would consider upgrading front and rear shafts. I won’t throw out recommendations as I’m not entirely familiar with everything out there. I run RCVs in the front and stock in the rear on 37”.

I will say one thing I do wish I had with 37” tires is at least a PSC big bore or even Hydro assist. Good grip & tight spots don’t bode well for me. Turns into an Austin Powers skit.

Scott
 
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