Dana 35 Disc Brake Swap - JeepForum.com

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post #1 of 11 Old 08-17-2008, 07:47 PM Thread Starter
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1993 YJ Wrangler 
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Dana 35 Disc Brake Swap

Ok so I've gotten a fair amount of support for a full write up on this swap so here goes.

Easiest and cheapest way I'm aware of is using the setup from a Grand Cherokee with a dana 35(non v8). Just like this one.

When you break down the zj 35 you want to grab just about the entire brake setup. This includes the calipers and pads, rotors, brake hose and banjo bolt, and the backing plate(which includes the e-brake setup) if you plan to setup and ebrake with them get the e-brake cables too.

backing plate

calipers, you can see i cut the hoses because when i got them out i didnt intend to do the swap myself, i was just going to sell the calipers, save yours

rotor, its rusty but i wire brushed it clean and it works just fine

old bent housing from a wrecked zj

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post #2 of 11 Old 08-17-2008, 08:13 PM Thread Starter
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Next step is breaking down your old axle. Once you take your tires off, the drum itself should just slide off, mine was very rusty and seized up a bit so it took some persuading of a hammer and pry bar.

Now you have access to your axle shaft. To get it out (if you have c-clip axles) you have to take off the diff cover. spin the carrier by hand until you see the set screw holding in the pin that the upper and lower spider spin on. (silver pin in center) it should be a 1/4 12 pt and is a real pita. unscrew that and slide the pin out. Now you can push the shafts inwards enough to pull the c-clip off and then slide them completely out. Slide the pin back in when your done otherwise the spider gears can call out and are rather difficult to put back in place.

You're now looking at the internals of your drum brake system. If you have no intention of ever using these again or selling them or anything, just unbolt and rip it all out, you're not reusing any of it. The only part you may want to save would be the arm for the ebrake, depending on how you want to set up your new one. Don't forget the actual brake line in the back.

To get the e-brake cable out push the three tabs right at the mounting plate in and slide the cable backwards and out. Very hard to explain, easy to understand when you see it, i dont have a pic.

Now unbolt the mounting plate, its 4 nuts that are threaded onto bolts coming from the axle flange. Once you unbolt all 4 just grab either side of the plate and work it back and forth til it comes off. This can take some doing, mine was real rusty. (seeing a theme here?)

At this point your axle should be clear of all drum brake equipment.

As an afterthought, you dont really have to take everything off of the plate, just disconnect the brakeline and e-brake. I did because as i was tearing it down i had the intention of rebuilding my drums but decided to return all the parts and just go disc.

Last edited by willhf1011; 08-18-2008 at 03:28 PM.
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post #3 of 11 Old 08-17-2008, 08:39 PM Thread Starter
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Now its time to start putting stuff back together. I have less pics of this.
Start by bolting up your backing plate. I hope you marked right and left, though it doesn't really matter, i think they'll only fit one way. Once you get them all squared away, slide your axle shaft back into the housing. If you can stick some grease on the end and be very gentle as you don't want to damage any of the seals. once thats all the way in where you want it put the rotor on and then slide the caliper (and pads) onto and bolt it to the backing plate.

Now that your caliper is on you can hook up the brake hose and measure out/plan where you want your lines. If you want i think you can reuse the stock lines and screw them into the end of the hose. I replaced all mine and bent up new ones because mine were....rusty. if you're going to reuse yours you're going to have to bend them and massage them to fit the hose as the hard lines for drum brakes are a few inches longer than for discs with the hose. Find some method of fastening the hose to the housing (i used a hose clamp)

You should be more or less ready now so bleed your brakes (make sure you put the calipers on the correct side so the bleeder is on top) check for leaks, and go take a test drive.

At this point you're pretty much done the disc brake swap. If i missed anything (which is very possible because i did this swap over a month ago and just wrote this up from memory) or if you want more pictures/have a question on a certain aspect of it just post up. The next post of two of mine will be regarding my master cylinder and booster swap.
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post #4 of 11 Old 08-17-2008, 09:18 PM Thread Starter
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So what led me to a master cylinder swap was actually just me being stupid and making assumptions that were incorrect. After i did my swap i had very little pedal. Bled and bled and bled the system and couldn't figure it out. I just assumed that with the discs in the rear now my master cylinder wasn't pushing enough fluid and with my proportioning being set up for drums in the rear it was off. When i finally swapped out my MC i had the same problem and it turned out my calipers were no good. So my final say is that an MC swap is not necessary for the discs but if you have access to a ZJ setup its a pretty straightforward swap so if you're up for it swap it in. First i pulled out my MC and discovered that the ZJ MC was a little different setup. I'm sure that its possible to make the ZJ MC work with a YJ booster but i just decided to swap boosters too. The ZJ booster was dual diaphragm which gives you more assistance for the larger bore MC.

So if you're doing the MC swap as well obviously don't worry about bleeding your brakes when your done as you have to disconnect all your lines again anyway. You can either take the lines off the proportioning block or from the MC and reuse your proportioning valve. I don't remember which i did, i think i reused my block.

Once all your lines are off go underneath your dash and go to the top of the pedal where you will see a clip holding the actuator arm onto your brake pedal, undo that and now you're ready to remove the booster. take the vacuum line that goes to the booster off of the intake and unbolt the 4 nuts that hold the booster onto the firewall.

This is the point at which some fabrication comes into play. Basically pushrod on the ZJ booster isnt long enough to reach the pedal on a YJ. Sooo, you have to lengthen it. What i did was cut about 4 inches off of my old YJ booster pushrod and just the tip off the ZJ booster. I used a die and cut threads onto the end of the ZJ booster pushrod, i don't remember what size though.

Then i found a long bushing whose inside diameter was the same as the outside diameter of the peice i cut off of the YJ push rod (getting confusing enough yet?) I welded a nut that matched the threads I cut onto the bushing and then slid the YJ rod into it.

Theaded that onto the ZJ booster pushrod. I mounted up the booster separately from the MC as it was easier to adjust the throw of the pedal like that. Once the new pushrod is coming through the firewall see how much longer or shorter it needs to be to hold the pedal out all the way, a YJ brake light switch works in opposite of alot of other types, when you push the pedal is releases a switch that then sends current to the relay whereas alot of others depress a button as you step on them. So the point of that is that the pedal must be all the way out otherwise your brake lights will be forever on. I used washers to shim my rod but you can find the difference and then weld it or thread it all the way out of however you please, it really doesn't matter too much, just so long as it works.

Once you get your pedal all set just go ahead and bolt the MC up to the booster, hook up the vacuum line and connect all your brake lines (make sure you get the right ones in the right spots) and bleed. I suppose it may be better to bench bleed the MC but i did not and it works fine for me.

Now that i swithced over to the new booster and MC I can lock up my front tires (32's) no problem on pavement, i don't think i could do that with my stock setup with stock tires.

If you need any more info or pictures of anything in particular just let me know. I know the second half of this was a little scarce on pics my internet just got very slow and i got tired of uploading pictures. Post up if you want more or certain things, ive got a lot of them.

Questions anyone?
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post #5 of 11 Old 08-18-2008, 08:18 AM
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Nice work and thanks for the write-up! You put a lot of work into that, and we all appreciate it.

Now I add another item to my long list of to-do mods........

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post #6 of 11 Old 08-18-2008, 11:37 AM
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This is great. I was actually considering doing this to my YJ as well. Now I've got some knowledge on how it's done. Doesn't seem to hard either. Thanks a lot man.
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post #7 of 11 Old 10-15-2008, 03:22 PM
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does it matter what year zj to get ? im gonna use all new brake hose and banjo bolt and calipers so i was just curious. thanks

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post #8 of 11 Old 10-15-2008, 06:45 PM
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Yes, I'm also curious what year(s) to look for & do you know that this will work on a d35 with bolt in axles as well. GREAT POST & WRITE UP. These things help out so many !!!!!!
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post #9 of 11 Old 10-15-2008, 08:39 PM Thread Starter
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Any year ZJ with a dana 35 should work fine. I think the ZJ's ran from the early 90's to the 97 or 98. The years may be a little off but its somewhere in there. As far as i know it will work on any YJ dana 35 and i suppose it may work on TJ 35's as well.
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post #10 of 11 Old 03-06-2011, 07:21 PM
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bump great rite up
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post #11 of 11 Old 03-06-2011, 10:38 PM
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subbed for future reference.

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