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  #1  
Old February 5th, 2012, 01:19
anthrax323 anthrax323 is offline
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KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

I was fortunate enough to find a set of rear disc brakes off a 2004 KJ (Liberty) for $200 in excellent condition locally (pads and all, including Bosch rotors), and dedicated today to getting everything installed. This topic is sparsely covered and has many opinions/options, so I figured I'd write this up for the future reference as others (especially as more and more KJs will find their way to pasture in the coming years).

What you need
  1. KJ backing plates (and E-brake hardware)
  2. KJ axle flange studs (splined, hammer out with a mini sledge)
  3. KJ rotors
  4. KJ calipers
  5. KJ parking brake cables (rear L/R only)
  6. XJ front wheel studs (x10)
  7. WJ rear brake hoses/soft lines
Basic information
  • XJ hard lines are threaded 3/8-24
  • KJ caliper banjo bolts are threaded 3/8-24
  • KJ brake hose blocks are 1/2" thick, as are the WJ's
  • Brake lines must be bent rearward (180 degree U in my case) and soft lines must be routed down-and-up in order to clear the caliper bolts and bleed valve
Additional information
  • KJ soft lines cannot be used, as they are permanently fused to the hard lines. I have not examined the 2006 model which is rumored to have threaded unions, so that is a possibility.
  • The E-brake cables are a direct fit, and the driver side is indeed far longer than it needs to be. If you don't want to have a custom cable made (or have it shortened), it can be looped in the space near the shock crossmember.
  • TeraFlex sells soft lines specifically for this application, including weld-on tabs for the soft-to-hard line union for around $80 (and based on pics, I genuinely believe their kit uses KJ parts). WJ lines cost about $12/ea.
  • Modification of your proportioning valve is not necessary. Brake power is perfectly balanced front to rear.
All in all, this project cost me just under $300 and has made a HUGE difference in the braking performance of my XJ (not to mention got rid of a mysterious rattle and occasional loud pop, which were ultimately due to f***ed up drum brake assemblies). I just can't believe it took me this long to pull the trigger on it.

If you want pics of any aspect of it, please let me know and I'll get them up.
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  #2  
Old February 5th, 2012, 05:18
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1985xjlaredo 1985xjlaredo is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

Yes Lets get some pics up! Then this could be worth a sticky
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  #3  
Old February 5th, 2012, 06:16
stumpXJ stumpXJ is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

I have liberty brakes on mine as well, although I did not put them on, the PO did. Thanks for the write up, I wasnt sure what all was used. They do work well though! Do all year Liberty's work for this? Or just the 04?
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Old February 5th, 2012, 10:23
anthrax323 anthrax323 is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

I didn't take any pics during the install, so I can only post post-install pics if desired (E-brake and hydraulic line routing primarily). The installation process has been covered ad-nauseum already, so hopefully people can fill in the gaps.

Stump - as far as I know, the donor can be any year KJ (02-07), however, I don't know if the KK discs will fit. That model is too new, and parts are more expensive. It does use the 5 on 4.5" lug pattern, so if it also uses an 8.25... Maybe?
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Old February 9th, 2012, 14:30
Redsnake Redsnake is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

Thanks for writing this up... obviously any pics (even post install) are helpful.

I'm not 100% sure, but I believe some of the early model, or perhaps all 2002 KJ's had drums on the rear. My wifes '03 Liberty has discs. Wonder if she'd notice if the rear brakes were all-the-sudden gone... Ha.
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Old February 9th, 2012, 18:03
stumpXJ stumpXJ is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

I think the PO said mine were from an 03.

~ Stump
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  #7  
Old July 25th, 2014, 21:29
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photondisruptor photondisruptor is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

Old thread time! My rear drums are shot, and I'm looking to upgrage to disks, currently I've got a D35 w/3.55. I found a KJ 8.25 w/4.10s for $400 in a nearby yard, is it possible to swap in the whole axle?
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Old July 25th, 2014, 21:56
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yossarian19 yossarian19 is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

Possible, yes. Practical... less so.
The KJ has a coil spring rear suspension and is wider than the XJ 8.25 as well. The brake lines will also be different.
So you'd have to cut most / all the brackets off, weld new perches / shock mounts on, re-plumb the brakes (I'd think) and be OK with the extra width (don't recall how much)
You'd probably be into it for $600 all in.
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  #9  
Old July 29th, 2014, 00:45
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OutkastBoss OutkastBoss is offline
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Re: KJ (8.25) rear disc swap - Clearing the air (semi-writeup)

Here is my rear disk conversion, there a re a few pics.

http://www.naxja.org/forum/showpost....5&postcount=73
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