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Discussion Starter · #1 ·
The '98 XJ 4.0L with AX15...

  • 31" BFG KO2's on 15" steel rim
  • Front and rear Smitty Bilt XRC bumpers
  • Smitty Bilt XRC 9.5k winch
  • Near full roof rack
  • 3" lift
  • Extended rebuilt driveling, for the 3" lift

So, what do you all think would be a regear setup that would work for this winter daily driver?? Or should I just keep it the way it is??
 

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The easiest and cheapest thing I think is to obtain Axle assemblies from an XJ with an auto tranny. Use 97 and up with Chrysler 8.25 rear end. You have a 3.07 ratio now an those have a 3.54 ratio, which is just about right for the 31" tires
 
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Discussion Starter · #3 ·
Sounds like I'll be searching for what you suggested. Thanks for the heads up on this.

BTW, badass engine you have there!! I was looking at a stroker from 505 for mine. Is that what you have??
 

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No I have the Chevy V6 truck engine. However it is coming out and going on steroids soon
 
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I definitely agree with 4.3L XJ, that would be easiest and direct swap for you to do. Re-gearing is always in my opinion the best mod you can do to your jeep. If you don't want to swap axles but just want to go with actually re-gearing. My advice would to choose the lowest ratio you'd eventually want to be at. Just do it once and be done. I have 4.56 ratio in my jeep but wished i would have done 4.88 or even down in the 5 range. As you add weight with wheels and tires, and all the metal add ons to the body, the gearing will definitely help.
 

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I have an AX15 also and have done the axle swap to 3.55 gearing out of a auto. With 31's it will be spot on. And it's pretty simple. When I did that I went ahead and jumped up to 33's and it was manageable (not perfect but ok) then I stumbled across a set of axles with 4.10s and did the swap again. Made things a little better but 4.56s gears will be much better. I have been saving my pennies and am real close to calling the shop that has done work for some friends and pull the trigger on the gears and lockers.
Good luck on your search.
 

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Discussion Starter · #7 ·
Is it just me or does it look like someone already put in a Chrysler 8.25 in the rear end.
 

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Discussion Starter · #9 ·
I was able to get the entire build sheets for the XJ, from the Dealer yesterday.


Looks like she did come with a Chrysler 8.25 with 3.07 gearing in the rear end. This sounds good, but which would be better...getting a Chrysler axle out of an automatic that already has 3.55 or swap out the gearing in the 8.25 I already have in it to 3.55??
 

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And cheaper!
You can find a set of axles, 8.25 and high pinion dana 30 with 3.55 gears pretty reasonably. Where the cost for the parts and labor could be 4 times as much. If you go with just re-gearing, go ahead and install 4.10s to match up with 31" tires perfectly.
3.55 gears will only make things better.
 

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Discussion Starter · #12 ·
Part would be my only cost as I do everything myself.

So if I decide to go 4.10's just regear and not replace the axles??
 

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One of the most complex jobs on a jeep is to regear. It's not really hard. I have done several, but it is an EXACT science. You are talking measurements in the thousandths (.001) and it requires a few special tools. And LOTS AND LOTS of PATIENCE. the only way to know if gears are setup properly is to read paint markings on the mesh pattern between teeth. To achieve this may require assemble and disassembly a dozen times. I am not trying to scare you, but yes I am. Gears are expensive and can be ruined in a few hundred miles if not installed correctly.
Search YouTube for regear videos. The place is loaded with them. The last set I did, I pulled the carrier out 9 times.
I also know finding 4.10 axles is hard. They are out there, just hard to find. 4.56 was never a stock ratio. I changed mine years ago and couldn't be happier.
 

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Yes , it would be best to re-gear to 4.10 s cause that is the optimal ratio for you tire size. Would need a new carrier for the Dana 30, I'm not sure if the 8.25 has a carrier break or not. I think you can get gearing sets for around 1k and the master install kits are about $125 each. So your cost is going to be aprox 2 grand to regear.

Where as you can get a set of axles with 3.55 gears for between $250-$500. And have pretty good results. Just not as good as 4.10s
 

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One of the most complex jobs on a jeep is to regear. It's not really hard. I have done several, but it is an EXACT science. You are talking measurements in the thousandths (.001) and it requires a few special tools. And LOTS AND LOTS of PATIENCE. the only way to know if gears are setup properly is to read paint markings on the mesh pattern between teeth. To achieve this may require assemble and disassembly a dozen times. I am not trying to scare you, but yes I am. Gears are expensive and can be ruined in a few hundred miles if not installed correctly.
Search YouTube for regear videos. The place is loaded with them. The last set I did, I pulled the carrier out 9 times.
I also know finding 4.10 axles is hard. They are out there, just hard to find. 4.56 was never a stock ratio. I changed mine years ago and couldn't be happier.
I found a set 4.10s for $500, I was very lucky! And it was the second time I swapped axles. But I'm still wanting 4.56 gears for my 33's
 

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Discussion Starter · #17 ·
You are all freakin awesome!!

The best part if me doing jobs like this, extremely technical, is the fact that i'm an Engineer and the mind can build anything. And my best bud is the best Machinist in the NW. He's done many of these, just not on off-road setups. I help him build extremely high performance engines/transmissions and he helps me with jobs like this. But the real credit truly goes to you guys for the knowledge and guidance in this realm. And I can be very patient in making sure everything is perfectly dialed-in before use.

Thanks again!! Don't hesitate to stuff my brain-housing-group with more knowledge, i'll soak it all up.

-Semper Fi
 

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Just my 2 cents here. Now is the time to decide if you want lockers, limited slip etc. Much easier when you have it out and on the bench
 

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(y)
 
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