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XJ D44 rear disc options

blistovmhz

NAXJA Forum User
Location
Vancouver, BC
I've got what I believe to be an XJ D44 rear under my 98 XJ. I say "I believe" because the previous owner had no idea where it came from, and I haven't found any definitive numbers to prove it's from an XJ.

Anyhow, my drums asploded and it's time to assess my brake options. I've got a set of KJ rear discs bolted to my 8.25 right now, which I was considering bolting to my 44. The backing plate holes don't line up, but I think I could get away with drilling a new set of holes to line up with the 44 axle studs, and order a new set of axle retaining plates to use as spacers on the back.

That said, I don't know how the KJ rear discs will compare to the 10" drums that were on the 44. Anyone know? Hell, anyone know if any of the D44 rears used different backing plate hole spacing, or are they all the same?

8.25 spacing is even between both top bolts and both bottom. My D44 has the top bolts set a bit wider apart and the bottom two a bit closer together.


And, at the end of the day, what's the best brake to be running on this axle? Should I bother fitting the KJ discs in, or should I go for an exploder set, or just find a new set of drums?
 
Explorer with ZJ discs is pretty easy, and the holes in the backing plates need to be elongated to the inside. Search Dana 44 Rear disc, I did a howto on this years ago.
 
Explorer with ZJ discs is pretty easy, and the holes in the backing plates need to be elongated to the inside. Search Dana 44 Rear disc, I did a howto on this years ago.

Yea, I'd read through it, and again just now. Those explorer back-plates look suspiciously similar to the KJ's I already have, other than the hole spacing. The rotors from the KJ require no modification as the center hole was setup for an 8.25 (stock).

The only two issues I have with the KJ discs on the XJ D44 is that the hole pattern is different (which you'd shown in your writeup) except that it's more exaggerated on the KJ backplate. I'd have to give the whole plate a spin about 15 degrees and drill new holes, but I don't have access to a machine shop so trying to figure out how to get the holes lined up perfectly.
Second issue is the same as your setup. I need a spacer to push the back-plate out about 1.5-3.0 mm from the axle. Was thinking of just ordering a set of rubi axle retainer plates and stacking them inbetween the axle tube and back-plate.

This sound about realistic or am I missing something else?
 
How big is the wj disc brakes?

No idea. I know the ZJ's aren't as beefy as the KJ's though.

Also, I just realised that the KJ's may not work because when I add the spacer between the axle and the backing plate, I'll get the shoes aligned with the hat, but I think that may prevent the axle from seating into the tube properly. Grr.
 
You could get the wj disc brakes with dual piston calipers. I think their a inch bigger than the xj with slotted rotors. Just my 2¢. :D theirs a how to video on YouTube. Just type in Jeep xj upgrades scroll down till you see a wj brake rotor. Or type in his name martinbuilt. He shows the steps.
 
You could get the wj disc brakes with dual piston calipers. I think their a inch bigger than the xj with slotted rotors. Just my 2¢. :D theirs a how to video on YouTube. Just type in Jeep xj upgrades scroll down till you see a wj brake rotor. Or type in his name martinbuilt. He shows the steps.

Looks like a fun mod, but I JUST redid my front brakes and they're fine. Looking for rear disc options on the XJ D44. There are tonnes of options out there, but none that I've found yet that don't require fabrication just slightly beyond my or my garages ability :p
 
BTT because I think you missed the above post because you were typing when I posted the reply.
 
BTT because I think you missed the above post because you were typing when I posted the reply.

Problem with all the kits I've found is that none of them actually use the same bolt spacing to the axle. They're all the offset spacing used by the 8.25. The D44 spacing is equal top and bottom while the 8.25 and D35 have shorter spacing on the bottom and wider on the top.

Now I've got my KJ backing plates all drilled out and mounted and EVERYTHING is working perfectly except I need those axle bearing preload spacers, and Teraflex wants almost $100 for a pair with shipping, and the product description doesn't say if the the taper is just on the inside or both inside and out. Their PN: 86261 is the one I KNOW would work, but it's no longer in production. They pointed me to 86262, which shows 3" OD, which is too big if that OD is on both ends. Seems no one there was able to confirm if the seal side was tapered on the OD as well. Not spending $100 on the wrong part, then paying another $50 to ship them back :). So I'm hitting a wall in each direction.

Trying to find something I can fab up for that spacer myself now. Maybe sticking another seal behind the retainer plate?

That said, anyone know where I can get the correct spacer?

*edit*
Well crap. Called Teraflex to ask about the two PN's, and turns out the one that says out of stock and no longer in production on the website, is in stock just fine and only $6 each. Got both, with 2 day shipping for $24.
Maybe this is why no one trusts the internet :p I always forget to just phone about parts instead of relying on redneck websites. durp.

So, this problem is solved. Will have an update here shortly. If it all goes together, this is the easiest D44 rear disc upgrade option (KJ 8.25 rear disc). The only modifications necessary were to drill out new holes in the backing plate, enlarge the rotor center hole by about 0.008", and throw in some $6 spacers between the retainer plate and seal.
 
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Fine. I understand that you have solved your problem. That is great. But had you bothered to check out the link, you would have found that this is no ordinary conversion kit. This is relatively new and is the only disc conversion for the factory XJ Dana 44 that is completely bolt in, no modifications needed, everything is included, no extra spacers or things to track down. Bigger and beefier discs, too. Better braking than the usual conversions. Lots of options too.

Just trying to help :wave:
 
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Fine. I understand that you have solved your problem. That is great. But had you bothered to check out the link, you would have found that this is no ordinary conversion kit. This is relatively new and is the only disc conversion for the factory XJ Dana 44 that is completely bolt in, no modifications needed, everything is included, no extra spacers or things to track down. Bigger and beefier discs, too. Better braking than the usual conversions. Lots of options too.

Just trying to help :wave:

I'm not arguing. I just already had almost everything I needed, and just needed to track down a spacer. Doesn't make sense to me to buy a whole other kit when the one I have is 95% complete and I already know it'll bolt right up.
I've installed other conv. kits before and the one thing they always seem to have in common, is that if you have one bolt pattern, the kit will have the other one :)
 
Not that it matters any more since you've already ordered the Teraflex spacer, but the retainer plates from a TJ Rubicon 44 will work as well as long as you weld and redrill for the XJ44 hole pattern.

I have Crown Vic brakes on my 44 and originally ran the Teraflex spacer but have since converted the shafts over to the Rubicon backing plate. Sealed better and got rid of a slow oil leak. You're running different brakes so it may not be an issue.
 
Not that it matters any more since you've already ordered the Teraflex spacer, but the retainer plates from a TJ Rubicon 44 will work as well as long as you weld and redrill for the XJ44 hole pattern.

I have Crown Vic brakes on my 44 and originally ran the Teraflex spacer but have since converted the shafts over to the Rubicon backing plate. Sealed better and got rid of a slow oil leak. You're running different brakes so it may not be an issue.

I was considering the Rubi retainer plate, but didn't want to spend the money on new bearings/seals/retainer rings when I wasn't sure if these KJ backing plates would even work. Once they're on, I'll do more measuring and probably tear it back apart and throw on the ruby retainer plates, as my stock plates are sorta bent up anyway. Then'd be a good time for bearings and stuff.
 
I'm not arguing. I just already had almost everything I needed, and just needed to track down a spacer. Doesn't make sense to me to buy a whole other kit when the one I have is 95% complete and I already know it'll bolt right up.
I've installed other conv. kits before and the one thing they always seem to have in common, is that if you have one bolt pattern, the kit will have the other one :)


Oh, sorry, I wasn't arguing either. I just re-read my post and it did seem a little mean, that was not my intention. I am a slow typer and I try to keep my posts short and to the point and sometimes they seem blunt.

Anyhoo, I understand your situation and I would have gone the same way since you already have the hardware. Makes perfect sense. With that said, you stated in your OP and in posts afterward that you were looking for options. I myself have also been looking for a true bolt in big brake conversion for my factory Dana 44 axle and have been met with the same problems that you have encountered with having to somehow modify any of the kits available and even with putting together the ZJ, WJ, or Kj brakes or the Crown Vic brakes, etc...

The 2 problems that I had run across after having done tons of research have been not only the having to modify all of the above options, but also that when the conversion has been done, most people state that it was either no better than the drums or not much better.

That's when I finally came across the company in the link above after talking with another manufacturer. Finally, a true bolt in option for the factory Dana 44 with larger, vented rotors and many options and uses factory calipers (GM) with the option of hydraulic or manual parking brakes that you can find at any auto parts place and they even have the short brake hoses needed and you have a choice of rubber or stainless braided. This is what I'm going with.

But when you replied and said that you did not want to mess with the many kits because of the modifications (bolt spacing, center hole diameter, spacers, etc...) I realized that you had not looked at that particular kit because there would not be any mods to be done to it. I was fairly excited about finally finding a good disc brake conversion for our kinda rare axle and wanted to share with you and anyone else looking for such a project. That's all. And no, I don't work for the company even though this post has turned out to look like a commercial, lol.
 
Okay. Everything is installed and (mostly) working.
I messed up and clocked the backing plates backwards instead of forwards, which put the calipers way below the leafs, which I don't like as I tend to bash the hell outta stuff. I clocked them backwards to keep the e-brake cable pointing up over the spring, but after I saw the caliper position, I re-drilled the plates clocked forward. This has the e-brake cable coming out just below the leaf, but I'm not too worried as they tuck up nice.

Having and issue though and hoping someone has an answer.
I had these brakes installed on my 8.25, and they FELT better than the drums, but I never really tested properly.

This time however, I jacked the rear end up on stands, started it up and let it idle in gear to test brakes. For some reason they won't even stall the motor. I bled the crap outta them but nothing doing, I can't get much stopping power to the rear. I suspect I may have let some air into the MC, but I took it for a test drive and I've got plenty of stopping power in the front, but doesn't seem like any in the back.

I've never had to bench bleed an MC on the Jeep, so I've no idea if there's somewhere air could get in and only give me problems with the rear. Any idea's? I figure I should be able to lock up all 4 at this point. Stops pretty fast, but not good enough when you drive in Vancouver, the land of new Chinese drivers who are driving on what they call "a family driving license"... :) (no shit. some woman was selling "family licenses" at the registry, only recently got caught. No driving test whatsoever....)
 
Did you take the internals from the KJ proportioning valve and install them into your XJ proportioning valve? When you go from rear drums to discs, you need more brake line pressure to the rear discs. There are 3 ways of doing it;

1- internals from from the KJ proportioning valve and install them into your XJ proportioning valve.

2-Take the whole KJ proportioning valve and installing it into your XJ.

3-Get rid of your proportioning valve and plumb in an adjustable proportioning valve from Jegs or Summit racing or etc...
 
You aren't experiencing prop valve issues and the common prop valve guts come from a zj, not a kj.
Check if your bleeder screws are pointing up or down on your rear calipers. If the point is down you'll never get all the air out.
 
You aren't experiencing prop valve issues and the common prop valve guts come from a zj, not a kj.
Check if your bleeder screws are pointing up or down on your rear calipers. If the point is down you'll never get all the air out.

:) Bleeders are pointing up :p
Grabbed the prop valve from a disc/disc ZJ and swapped internals.

On the subject of prop valves and how they effect brake balance, it seems there is some confusion about what they do and when.
The prop valve has ZERO effect on light/medium braking. It only engages under high pressure, hard braking, and it's function is to LIMIT rear brake pressure to reduce rear lock-up. Now that I've already done the swap, I guess I'll leave it in, but so everyone knows, the swap is not going to increase rear brake bias, but will instead reduce it under hard braking.
The XJ MC is a twin piston design. The larger piston is for the front brakes and the smaller is for the rear. In some swaps (probably nothing you'd do on an XJ) the rear MC piston may be too small to fill the larger rear calipers. From what I've found online though, there's no caliper you're going to fit on an XJ d44/8.25/d35 that will have such a high volume as to require a MC swap. Maybe with a d60 rear.

I'm starting to suspect it may just be glazed pads. Took a look at them last night and they are a bit shinier than I'd like. Will try baking and sanding them and clean up the rotors and see if it makes a difference. Overall, my braking is pretty darn good as it is, but I KNOW the rear isn't contributing as much as it should.
 
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