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Rear Disc Brake Conversion
 

NOTE:  This conversion alters one of the safety devices (the brakes) on your vehicle.  If you should decided to undertake this conversion, it should be performed by personnel who are competent to conduct such alterations to a vehicle.  This conversion can result in changes to your vehicle's handling and braking ability.  This is not a step by step set of instructions on how to do it, but rather a summary of the various things I did to accomplish my conversion.  Any similar conversion work performed on your vehicle is done at your own risk.
 

Somewhere along the way, I got wind of a little mod that ended up on my California buddy's TJ, which would just happen to be Robert Yates.  Robert's TJ was something of a test platform for this rear disc brake conversion.  A mutual friend had done some axle work on one of his TJs which sparked the idea for a rear disc conversion on a TJ's Dana 44 rear axle.  Robert's TJ was the first candidate to get the conversion....I guess you could say it was the prototype.  The results made Robert a happy camper.  On a side note, online universities or online colleges for programs pertaining to these simple conversions and modifications might be hard to find in online land. If you are super comfortable with things like brake conversions as well as brake modifications to your Jeep and want to further your education, online universities might be the way to go.

I saw some pics posted on a web site and read some of the comments written by Robert.  I was impressed to say the least and decided to give it a try, if at all possible.  So....I found myself scrounging for parts.  I posted an e-mail on the local club e-mail reflector and found some parts from another Arizona Jeeper.  I needed the rear disc brake assembly from a '95  to '98 Grand Cherokee's Dana 35 axle.  After receiving the D-35 brake parts from a '94 Grand Cherokee (hey, it was close), I visited the local Jeep dealership to acquire a few new pieces for the disc brake assemblies.  Some of the e-brake parts were missing and I needed to replace them before we could start on the project.  I can tell you that getting these parts from the Jeep dealership is rather pricey (I know, tell you something you don't already know).  OK....what I found out later was that I could get a complete hardware kit, which included all of those little parts that are used in the e-brake assembly (clips, pins, star adjuster, springs, etc....all of them) from a good brake parts warehouse.  Just ask for a hardware kit and you'll have all those nice new parts to replace the old rusted ones you get from the donor vehicle.  (been there, done that....spent too much money at the dealer!)

Basically, this is what I used:

    complete ZJ rear disc assemblies including e-brake cables
    two bearing retainers
    new seals for axle shafts
    new custom axle backing plates
    eight 3/8 x 1 1/4" SAE fine thread bolts in grade 8 and upset lock nuts 
    Currie brake hose kit

 

Christmas 2001 was coming up and I arranged to camp out in Robert's back bedroom for a few days while I worked on the brake project.  Besides tapping some of the fab experience from my SoCal buddy, it was a good opportunity to visit some of my friends that I hadn't seen in a while (and some that I had yet to meet!).
 

I had already wire brushed and sanded down the dust shield, mounting brackets, and disc rotors.  A coat of primer and some flat black paint rounded out the pre-mod work.  I mic'd the rotors to ensure they were still within minimum standards for rotor thickness.  The calipers were in pretty bad shape and rather than deal with a rebuild kit, I opted for rebuilt units.

To help improve the overall performance of the TJ's brakes, I was told to get a set of Performance Friction disc pads for the front axle.  A trip to the local AutoZone parts store netted me these necessary front disc pads.  The remaining odds and ends would be waiting for me in California, so I headed out to CA for a LONG weekend with high hopes and most of the necessary parts loaded into the back of my TJ.
 

The key ingredient to making this whole thing work, aside from having a buddy that loves to fab TJ projects, was the non-existent axle retainer plate (seen in above pic sitting in the middle of the dust shield..  For this conversion, the retainer  plate would anchor the disc caliper bracket to the axle flange.  It would also hold the dust shield in place, which in turn holds the parking brake assembly. 

It is important to use the new axle retainer, as it is needed to compensate for the thickness difference between the stock backing plate and the thicker cast bracket. It also provides the correct pre-load on the axle bearing that sits at the axle flange.  Without a properly fabbed axle retainer plate, this conversion will not work for you.

My SoCal buddy had a few of these manufactured....you know how it is....he knows a friend who does machine work, and then he took them to another friend who did some more work,  and then he had them zinc plated, etc.  Well, you get the picture. 

NOTE:  Here are some comments from my buddy in CA who made the retainer plate.  He posted this to an on-line forum on 1-13-2003:

I was involved in machining the custom retainers. I saw an '03 with discs on a lift and noticed that the rear discs on the 44 were identical to the ZJ discs. I wondered how the factory solved the problem and how much it would cost. It's cheaper that you would ever guess and here are a couple of pics with the part number. 


 

My retainer is shown next to the factory one (factory on the right). The factory part number is 1-05083678AA. Two are required. Cost should be less than 6.00 for both.

NOTE:  Another Jeeper forwarded me a note that said his dealership listed the above part # as 5083678AA.  It took them a while to find what he wanted using the number previously mentioned.  Sounds like a different release of the parts list, or something like that.  Anyway, just a heads up that you might find it using either number.

So folks, you can thank the DC engineers for making an inexpensive alternative to the machine custom retainer.  While this won't make anything else any cheaper, it will allow anyone to now go and scour the junk yards for the ZJ parts and stop off at the DC dealership for the "custom part".
 

I got four retainer plates....two to convert my main axle shafts and two to convert my trail spares.  The above pic shows the new zinc plated retainer plate installed on a D-44 axle shaft.  It is located at the bottom of the stack, with the seal, the bearing, and the bearing retainer all sitting on top of it, just as it would be if using the factory back plate.  I want to say a big thank you to Jack at CTM Racing Products.  Jack was kind enough to let us use his machine shop for a few minutes so we could press on the axle bearings.  By the way, check out his site if you are interested in some top quality u-joints for your D-44 or D60 front axle.  Some of these recently shipped to a number of ARCA competitors. 
 

The ZJ caliper bracket center hole is just a bit too small to allow the axle seal to pass through it. Just a little bit of metal needs to be removed to allow for proper clearance.  This is not a critical measurement.  It just needs to let the axle seal slip through without catching.  Since the dust shield hole is the same diameter as the bracket hole, it needs to be enlarged as well.  It is easy to bolt the dust shield and bracket together with a couple of bolts and then enlarge the "holes" at the same time. 
 

We used a sanding drum that was mounted on the drill press. A couple of minutes and it was ready to go.  Use an oil seal to check for adequate clearance.  Note that the above photo only shows the bracket, less the dust shield, being worked on.  (ok, I admit that I forgot to take the picture while I was actually doing it so I tossed the bracket up there and snapped a picture later in the morning)

More Disc Brake Conversion

 

 

 

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