mikekaz1 Posted April 12, 2016 Share Posted April 12, 2016 so I have a mj d44 in my parts truck I plan on swapping over, now it already needs a brake rebuild (its old, rusty and has been sitting a looong time) should I just rebuild the drums, or do a disk conversion. I have a complete 98 ZJ rear axle sitting at my house, its pretty rusty also, but all there... is there a big difference between the ZJ conversion or a Ford conversion? and pros or cons to either? or should I just leave drums? I did a full 8.8 swap on my TJ and really never noticed a braking efficiency change... just gave a benefit of not packing with mud and water offroading. the MJ is and will stay a "pavement princess" so offroad conditioning really isn't an issue. ok rant over, Link to comment Share on other sites More sharing options...
Megadan Posted April 12, 2016 Share Posted April 12, 2016 If it's going to be a pavement princess, then rebuild the drums and call it a day. Unless you are going to be doing a lot of towing or heavy hauling with it on a regular basis, then that is about the only reason I could see discs as a benefit. Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 12, 2016 Author Share Posted April 12, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also sceptical Link to comment Share on other sites More sharing options...
Megadan Posted April 12, 2016 Share Posted April 12, 2016 It's not really about the braking increase as it is about thermal handling. When drums get hot, they expand away from the shoes and reduce braking force. Discs don't have this problem, and are a little more efficient at cooling. That is about the only real difference between them, and even discs can overheat and lose braking performance if you aren't careful. They are just less likely to have that issue. Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 12, 2016 Author Share Posted April 12, 2016 ahhh ok... any knowledge on the true differneces and/or pros/cons of the ZJ vs Ford conversion? Link to comment Share on other sites More sharing options...
89eliminator Posted April 12, 2016 Share Posted April 12, 2016 i threw some KJ discs on my 44. noticed a big change in braking. My MJ sees more time off road, then on. My drums would pack full of mud/sand/rocks and just detroy the shoes leaving me with hardly any braking force in the rear. Discs eliminated that problem. Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 12, 2016 Author Share Posted April 12, 2016 also, for the conversion besides the brake assembly, you need a flange adapter correct? is there any other equipment you need? Link to comment Share on other sites More sharing options...
89eliminator Posted April 12, 2016 Share Posted April 12, 2016 I redrilled the caliper mounts. you also need a spacer that goes between the caliper mount and axle seal. teraflex sells them, not sure if they still do or not. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 12, 2016 Share Posted April 12, 2016 Teraflex still sells the preload spacers although you may need to call them to get the correct ones based on your particular setup. When I swapped my D44 in I transferred the Ford Explorer disks I had on the old D35, but had to purchase new backing plates due to the axle flange difference between the D35 c-clip axle and the D44. The non-c-clip D35 has the same flange as the D44 does however. Link to comment Share on other sites More sharing options...
schardein Posted April 12, 2016 Share Posted April 12, 2016 Here is my 2 cents. I used to mud bog a full size K5 Blazer with a full floater 14 bolt rear axle. Mud destroys drum brakes. And tearing apart a full float axle to clean/rebuild once a month was time consuming. A disc brake conversion was best thing I ever did to that axle (the only thing, really). Never failed from mud and didn't have to dig into it to change the pads. And the discs provided a LOT more braking. But that was bad. The rear end would lock up first, and if you don't know what happens next... the back end and front end try to switch places! You want the front to lock up first, just before the rear. I installed one of those "dial" type pressure reducers, dialed almost all the way down (instructions said that was 66%) and it was perfect. Parking brakes. I've seen two types on disc brakes. One is the caliper itself has an arm that applies pressure to the pads. The other is a tiny drum brake assembly INSIDE the disc assembly. Neither one of these is as effective as a regular drum brake parking brake. It's a matter of surface area (compared to the smaller inside the disc setup), and the servo action of drum brakes (compared to lever actuated caliper). This could be important for a truck with a manual transmission pulling a trailer. Or rock crawling and big tires. These are both places where you want a no compromise parking brake, and the factory drum setup will be the best (with good parts and properly adjusted). So there are times when a disc conversion makes sense. I would stay away from disc conversions that use a modified (machined) disc. This is a wear item that will need replaced and now will be even more expensive because it is a custom part. Most drum brakes on vintage trucks like our MJs are cheap to rebuild. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 13, 2016 Share Posted April 13, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also sceptical What do you have for a brake booster? Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 13, 2016 Author Share Posted April 13, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also sceptical What do you have for a brake booster? on the MJ? factory :thumbsup: Link to comment Share on other sites More sharing options...
cruiser54 Posted April 13, 2016 Share Posted April 13, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also sceptical What do you have for a brake booster? on the MJ? factory :thumbsup: You will realize more braking improvement on your MJ by changing to a dual diaphragm booster and master cylinder from a 99 to 2004 wJ than by adding rear disc brakes. Link to comment Share on other sites More sharing options...
xjrev10 Posted April 13, 2016 Share Posted April 13, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also sceptical What do you have for a brake booster? on the MJ? factory :thumbsup: You will realize more braking improvement on your MJ by changing to a dual diaphragm booster and master cylinder from a 99 to 2004 wJ than by adding rear disc brakes. Or do both and have pure braking awesomeness. I have ZJ rear discs in my 8.25, slotted rotors in the front and a WJ Master/Booster. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 13, 2016 Share Posted April 13, 2016 it does and will see heavy hauling. but I really haven't seen a braking increase on my TJ when I went from d35 drums to 8.8 disks.... so that's why I'm also scepticalWhat do you have for a brake booster? on the MJ? factory :thumbsup: You will realize more braking improvement on your MJ by changing to a dual diaphragm booster and master cylinder from a 99 to 2004 wJ than by adding rear disc brakes. Or do both and have pure braking awesomeness. I have ZJ rear discs in my 8.25, slotted rotors in the front and a WJ Master/Booster. I don't even have upgraded brake parts and the braking is awesome. But, I'll tell you guys this. I did rear discs on my wife's 88 and there was a big difference. Then added the WJ booster setup and it was twice the added braking effectiveness of the rear discs alone. On my MJ with a Dana 44 rear which has larger shoes, I just added the booster. I'm not so excited about doing rear discs on it now. Super big improvement alone. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 13, 2016 Share Posted April 13, 2016 You will realize more braking improvement on your MJ by changing to a dual diaphragm booster and master cylinder from a 99 to 2004 wJ than by adding rear disc brakes. Use a booster/master from a 95-96 XJ with the 1/4" spacer plate on your 91. Much easier, pure PnP, and works just as well. Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 13, 2016 Author Share Posted April 13, 2016 I have a booster from a 98zj already... would that work? I assume id still need the spacer? Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 13, 2016 Share Posted April 13, 2016 I'm not sure if the booster arm on the ZJ is the right length and the pedal mount is the same as the 95-96 XJ dual diaphragm setup. It may work w/o too much trouble, but :dunno: . The XJ unit is bolt-in; all you have to do is fab new brake lines from the distribution block to the master. I'm also thinking the 97 XJ and up setup should also work because the MJ firewall is the same. Anyone ever done this or know of it being done on an MJ? Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 13, 2016 Author Share Posted April 13, 2016 an eyeballs shot, the pedal mount looked the same on the ZJ, not sure on length though, I don't have an issue being a guinea pig seeing if it will work, worst case is I go "huh it won't work" and I go pull an XJ one. the trucks not my only vehicle so I don't care if its down an extra day or not. but its not exactly my top priority so who knows when it will get attempted either. Link to comment Share on other sites More sharing options...
Megadan Posted April 13, 2016 Share Posted April 13, 2016 I believe the ZJ and later XJ double diaphragm units are the same booster and master setup. It's the length of the rod from the pedal to the booster itself is where the only difference lies from what I remember. the ZJ unit has a shorter rod. I just wish I could remember where I found that tidbit of information. :hmm: Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 13, 2016 Share Posted April 13, 2016 ^^ I remember something like that too. I believe it was on the old - now defunct - Mad Maxx Jeep site. Link to comment Share on other sites More sharing options...
mikekaz1 Posted April 13, 2016 Author Share Posted April 13, 2016 zj has a shorter rod? someone refresh my memory... was the 95/96 spacer plate to compensate for enginebay/firewall clearance, or to better adjust/lower the pedal? or both? if it was just to lower the pedal then this may not be an issue.... and actually be easier Link to comment Share on other sites More sharing options...
Megadan Posted April 13, 2016 Share Posted April 13, 2016 The real question is how much shorter is the rod length. The spacer for the XJ is about 1/4" thick. I think the ZJ rod is more than 1/4" shorter than the XJ rod. Only way to know for sure would be to measure one of each and compare Link to comment Share on other sites More sharing options...
cruiser54 Posted April 13, 2016 Share Posted April 13, 2016 I believe the ZJ and later XJ double diaphragm units are the same booster and master setup. It's the length of the rod from the pedal to the booster itself is where the only difference lies from what I remember. the ZJ unit has a shorter rod. I just wish I could remember where I found that tidbit of information. :hmm: Nope. Link to comment Share on other sites More sharing options...
Megadan Posted April 14, 2016 Share Posted April 14, 2016 Nope to which part? Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now