Newbie Question on Tires/Lift/Gears? - JeepForum.com
 
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post #1 of 4 Old 08-14-2019, 08:34 AM Thread Starter
texasmark04
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Newbie Question on Tires/Lift/Gears?

Hello, new to forum and new to Jeep ownership. Purchased my first Jeep this summer, a 2017 JKU Rubicon 4 x 4. This is a 3.6L V6 Automatic with Dana 44 Front and Rear Axles. It has the optional add to 3.73 Front/Rear Axle Ratio. Came with LT255/75R17C BSW Off-Road Tires on 17" wheels, from what I gather pretty standard tires and wheels for this Rubicon.

Since the purchase, I wanted a more distinct stance with the suspension and wanted to move to 35" tires. So, I have added the following:
  • Rubicon Express 3.5" Lift Kit with Twin Tube Shocks - RE7142T
  • Nitto Ridge Grapplers 35x12.50R18LT
  • Mayhem 8090 18x9 Wheels

Had these all professionally installed by 4WP Parts Store here locally. I have not had anything chipped or changed the gears, everything else has stayed the same that came on the Rubicon when I bought it. Question I have is I have seen tons of posts on various sites about re-gearing and possibly having to upgrade axles or driveshafts. When I asked the guys at store, they said I didn't need to upgrade axles or driveshafts, but didn't mention anything about re-gearing. The more I read about this, the more I think this is something I need to do. Trying to get some opinions based on experiences forum members have, especially if anyone has setup similar to mine now. I have noticed when I drive the Jeep now, steering feels a little loose but not exaggerated like I have read about "death wobbles". I can keep control of Jeep with one hand on steering wheel, but wondering if there are items underneath vehicle that I should look at upgrading as well with this change.

By the way, using the Jeep as daily driver to and from work (about 8-10 miles each way), and of course weekend fun. Not hard rock crawling, but some small off-road trails and beaches (sand). So, not going to really run it hard off-road. Any advice would be greatly appreciated since I'm just jumping into this and loving all the modifications you can do to a Jeep. FYI, I have updated the sound system in the Jeep as well and very impressed with the setup I put together, if anyone is looking to upgrade, I can share my setup.

Thanks.

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post #2 of 4 Old 08-14-2019, 08:50 AM
222Doc
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3.73 gears is off for 35s on a 4 door. for best mpg/ better performance street. 4.56<min/4.88<tow, gear would be best. But this is rather expensive as well. i would think in the 2K range or more

Off road since the Rubicon has a very low low range of 4:1 it will do very well even with 3.73 off road.
you axles are fine.

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post #3 of 4 Old 08-14-2019, 09:04 AM Thread Starter
texasmark04
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Thanks @222Doc , so sounds like you definitely recommend re-gearing to at least 4.56 (4.88 preferred) for better MPG and better street performance. That is what I have seen as well, but was looking for some confirmation for my setup specifically. If I may ask, what all goes into re-gearing? Not sure I quite understand what all is involved in that, but must be intensive if is so expensive. Also, I have read about doing some chipping to help with bigger tires/MPG, any suggestions there?
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post #4 of 4 Old 08-14-2019, 09:51 AM
222Doc
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gears is a lot of work and it must be done with precision. , needs 2 new gear sets(front and back) they have to take both axles a part. i would guess its about 10 hours of labor?

programming your way out of this dont work very well. The main issue is in OD it cant hold that gear, its lugging so the trans drops to 4th when touch the gas. lift off the gas it then jumps back to 5th. Its called gear hunting, cant program your way out of this. Motor does the work and the trans send it to rear DIF. if the dif aint doing the work, the trans ends up trying too. THis in the end creates HEAT. Work=heat. if it works less, less heat.

Funny this happens so much too. People go big tires and then its sluggish, then they tune it since that tends to be cheeper. in the end it still gets poor mpg and still hunts gears. some get sick of that and just sell. then the next owner does gear it and NOW we have something. its geared right and its tuned. Now it can break the tires loose.

went through this when I bought my wifes SUV. 03 Excursion 4x4 7.3 TD. the owner lifted it, 35s 7 tune chip, turbo, Built trans, very expensive large shot injectors and more. BUT they never geared it. ran great but could not tow in OD and was just not all that quick consider what they did. First thing i did 4.30 gears from 3.73 diesels dont need as much gear so the steps are smaller when gearing these. BUt man it made a huge change. can tow in OD up hills of 6% now and its rather quick now. expensive yes it was since these 1 ton axles. I have setup gears but just did not want to do this one. was worth it though now those things he did can do the job since now the Difs are doing theirs.

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