Rear Disc Brake Swap /w Integrated Parking Brakes (Eldorado Calipers & 5-on-5" bolt pattern)

[boxyjeep]

I searched quite a bit to see if anyone had attempted this and came up empty so I thought it would be a good idea to share my experience.  I'm in the middle of a SOA conversion and have my rear Dana 44 axle pulled and thought this would be a good time to upgrade the rear brakes.

 

 

Up front I'm running WJ knuckles w/ WJ unit bearings/brakes as well as 5-on-5" bolt pattern JK-style wheels.  I'd like to avoid the use of bolt pattern adapters in the rear--I know this is an area of debate, but they are just something I'd prefer not to run.  Adapters also result in a wider rear track width than the front.  Not ideal.

 

I explored ZJ, KJ, and WJ rear disc swaps and really despised the need for the integrated drums and their backing plates that would need to be re-drilled for the Dana 44.  Many folks building larger custom axles will go with the mythical '79-85 Eldorado calipers with integrated parking brake.  Here's an example of a kit you can buy for a Ford 9".  I decided I would try to see if this was feasible.

 

 

My end goal was to run 5-on-5" bolt pattern axle shafts, WJ 12" front discs, Eldorado calipers, and some type of bracketry to tie it all together.

 

The first task was to re-drill my axle shafts to 5-on-5" bolt pattern.  This is a challenge for two reason: 1) there is an access hole that would need to be plugged, and 2) the flange diameter is too small to safely re-drill to the larger pattern.  To solve this I ordered a set of stock replacement axles from Dutchman customized with WJ flanges.  It may be possible to re-drill with TJ shafts or perhaps some years had larger flanges with more material, but that was not the case for me.

 

The second task was figuring out the bracketry.  Ruffstuff sells a few brackets for axles ranging in diameter from 2.75" to 3.5".  While the MJ/XJ D44 is 2.75" diameter, it steps up to 3.375" at the end of the tube.  When looking at the alignment of the caliper on the disc, it aligns most closely to the largest part of the flange:

 

 

The full-size axle kits are also made for 12.5" Chevy front disc brakes.  Since the WJ front discs are 12", that moves the caliper inward .25".  Based on these measurements, I ordered the 3.25" diameter Ruffstuff brackets.  I may need to shave these down a bit depending on fitment.

 

 

The next challenge is the preload on the seal and bearing.  Since the drum backing plates have been removed, that space needs to be filled.  I designed a basic spacer and will be using that to make up the approximate .14" thickness.  I suppose you could also cut out the center section of your drum backing plates.

 

I don't have the brackets in hand yet, but my goal is to attempt to align them with axle tube flange and weld them to the tube.  One potential challenge is ensuring that the tube doesn't distort around the bearing race.

 

I'll update this thread as the project progresses and will include all relevant part numbers and details.

 

 

 

[boxyjeep]

Reserved

[DirtyComanche]

Just a warning about those calipers.  Lots of guys wind up junking them and running the equivalent front caliper and ditching the parking brake feature.  They like to seize up and eat brake pads and rotors.  That's an inherent issue with their design, and the Isuzu calipers that are similar do the same thing.

 

I've been on and off looking for something that uses an electric parking brake caliper as it should be a more reliable option long term.

[AZJeff]

Dirty Comanche is on to something here.   The trend in designs has been AWAY from a mechanical parking brake being integrated into the caliper, and that's for a VERY good reason:  the system is not durable.   Corrosion and other environmental elements conspire to make the system less that totally reliable, and the cost to repair once it becomes jammed up with corrosion is costly.

 

I know a lot of guys think a duplicate drum-type parking brake running in parallel with a disc-type service brake is a waste of hardware, but the benefits of it's reliability outweigh the added hardware costs.

[DirtyComanche]

3 minutes ago, AZJeff said:

 

 

I know a lot of guys think a duplicate drum-type parking brake running in parallel with a disc-type service brake is a waste of hardware, but the benefits of it's reliability outweigh the added hardware costs.

Exactly.  The OEMs tried to get away with it using the caliper with the integrated mechanical parking brake, and it just didn't work right.  Hence it had a short production span for the Cadillacs, and same for the Isuzu, and same for any of the other examples out there (there is a handful more, and they are all as equally obscure).  They then mostly went to the "drum in hat" or a similar version of parking brake, as it proved to be much more reliable.  The only reason you can buy the Cadillac calipers is that there was so much demand from people trying to use them for rear disk brake conversions that it made sense for somebody (using a factory in China) to put them back into production.  There is a slightly better fully aftermarket version of them in the 4x4 aftermarket scene, I forget who makes them, but they're a lot more expensive and they still will fry the brake pads if used regularly.

 

The drum brake design works really well and lasts nearly forever as a drum in hat parking brake, so we've seen probably 30-40 years of it being used.  Now the push is to go to an electric parking brake, as the drum is something of a waste of hardware.  However, the OEM is looking at it from the perspective of producing millions of them over the lifespan of a vehicle's production, versus us with a "not wanting to bolt that on there" sort of mentality, they have the chance to save a significant amount of money in the long run so it is worthwhile to do the R&D for an electric setup.  The electric setup also saves even more money in there is no cables, no pedals or handles, and it can just be straight up integrated into the CANBUS architecture to automatically engage or disengage, and so on.  I suspect this will be the logical future for swaps once suitable caliper(s) are found, as the DIYer can just make most of them work with a toggle switch and (optional) indicator light.

 

I hate raining on the parade of someone who is already invested in something, but there's also something to be said for making someone aware of an issue before they get farther invested into it.

[75sv1]

MB used the drum in the rear disc for the W123 chassis. I have a 240D. Those look up that real well.  My Ford Contor SVT has external. I remember it working OK.  Also, the Ford 8.8 is about 3/4 shorter per side than a D35 or 8-1/4. I have used spacers. On my 4.5 on 5, I did and some spacers turned down to say 1" width. Then use longer studs. The use of the Yukon 8.8 axle upgrade should widen the Ford 8.8 1" per side. 

[ghetdjc320]

A tcase mounted parking brake is a nice option, then you can run a better caliper while having an awesome parking brake. A caliper based parking brake at the wheel has very little holding power and requires very little torque to breakaway. The parking brake shoes in the rotor hat is a better design due to the amount of pad contact area and the sort of mechanical “wedge” effect. It’s very hard to beat the parking brake of drum brakes but a tcase mounted brake comes close.

[boxyjeep]

Thanks guys—this is some really good feedback.  It seems like opinions on the internet are mixed on these calipers.  I am also at the point in the project where I can return things without incurring too much cost.

 

I’ll do a bit more research and see what might work best.  My concern about ZJ/Crown Vic discs is that the 5-on-5” axle shaft flange won’t fit the ID of the “hat”.  I’ll do some more research and update this thread.

[DirtyComanche]

I'd look at JK/JL or WK or other late model Jeeps with 5x5.  Some of that stuff might work, or be made to work.

[boxyjeep]

I ended up returning everything and buying a new set of drums and shoes for the rear.  I’ll use new longer universal e-brake cables (they were binding at full droop) and just stick with drums for now.  
 

As much as I’d like to be a trailblazer with this, the feedback in this thread made me realize that I’d rather just get the SOA done and the truck back on the road than spend weeks/months just trying to solve disc brakes…