Can I regear to 3.55?

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Libertard2k6

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I have an 06 Liberty 65th anniversary edition, my question is can I regear to 3.55 and would it improve mpg by much? I don’t do a lot of towing and mainly just use it for daily driving in rural Indiana
 

lfhoward

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I would advise against that. Running a larger tire size would essentially accomplish the same goal and I can say from experience (running a 30.5” tire) that gas mileage has NOT improved. The engine struggles in 4th gear on hills that would normally be no problem with stock gearing.
 

Libertard2k6

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I would advise against that. Running a larger tire size would essentially accomplish the same goal and I can say from experience (running a 30.5” tire) that gas mileage has NOT improved. The engine struggles in 4th gear on hills that would normally be no problem with stock gearing.
Large tire would improve my fuel economy?
 

Enorton5

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I'm about to go from running 245/75/r16 to 265/75/r16's so I'm preparing to regear and from what I've read you can not just change out the ring and pinion in the front diff of a 3.7 06 gasser, but that you have to change out the entire axle. That said would the front axle from a 2.4 gasser 02-05 be a perfect swap to the 06 3.7 kj.

 

nbas

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You need to regear front & rear diff. 265/75R16 is too large, as far as I know it will not fit under normal circumstances. 265/70R16 would fit instead of 245/75R16. I am running on 245/75R16 and I am very happy since I regeared to 4.10 (see my signature). i prefer 245/75R16 as it sits better on my stock rims, it has the same profile (compared to 265/70R16) without being very wide...
 

Enorton5

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I understand that you need to regear the front and back which is the basics so I felt I need not have to type it, and you still did not answer my question. Yes, a 265/75/r16 will not fit with no lift, but I have the appropriate lift. I understand that you prefer a smaller tire, but I do not.
 

lfhoward

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You’re asking if you can regear the front diff of your KJ or if you have to swap the whole front diff with one from a 4 cylinder KJ that is already geared to 4.10, correct? Ether way is fine. It tends to be easier to swap diffs rather than regear because a regear is labor intensive and typically costs a lot. 4 cylinder KJ gassers are getting harder to find, though. They were only made for a short time, and in low numbers.

Just some more regearing trivia for KK owners, if they read this thread. KK’s are a bit different:
- No KK’s came from the factory with 4.10 gearing, so a ring and pinion swap is needed with larger tires. (No diff swap option)
- KK’s can support 4.10, 4.56, or 4.88 gears. KJ’s can only go to 4.10.
- 4.10 is good for 31” tires, 4.56 for 32’s. We can’t typically run tires larger than that to make use of the 4.88 option.
- KK front diffs use the JK Wrangler Dana 30 ring and pinions, where as KJ front diffs use Dana 30-A gears only.
- KK’s and all but the earliest KJ’s have the Chrysler 8.25 rear diff. A few very early KJ’s came with a Dana 35 in the rear.
 
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nbas

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As far as I know, 265/75R16 will not fit even with a lift (I felt that I did not need to type it as you already have 245/75R16) under normal circumstances (I meant without further cutting...)
You can either change the front ring/pinion or swap a front diff from a 2.4 (what I did as I could not find front 4.10 ring/pinion in Greece)
 

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