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WJ Steering Knuckle/ Brake/ Steering Swap on My 5.9L ZJ

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  • WJ Steering Knuckle/ Brake/ Steering Swap on My 5.9L ZJ

    Over the weekend, I finally decided to knock out this knuckle swap, which I had been planning for quite some time. I ventured into some uncharted territory with this setup, and ran into a few issues that still need some attention before I call it done. I'm not sure how familiar people are with Jeeps on this forum, so here is a short list of things gained by doing this.
    1. Bigger brakes: Single piston calipers, and 11" (280mm) rotors make up the front braking system on the ZJ. The WJ is setup with 2 piston caliper, and 12" (305mm) rotors.
    2. Crossover Steering: The inverted Y steering system that comes on the ZJ works, but is less than ideal. Once lifted this system causes toe change throughout the suspension travel, and is generally always a pain to work with. The WJ's crossover steering separates the drag link from the tie rod, which eliminates the toe change completely.
    This picture shows the ZJ steering as it comes stock.
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    And this is the WJ steering.
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    I would say these upgrades alone are not worth the work, especially considering my Jeep is at stock ride height. However, I bought it 3 years ago, and it was sloppy back then. 50k miles later with no attention, pretty much everything was toasted. Tires were worn to the belts, wheel bearings were growling, ball joints were clunking, etc. I figured, if I was going to spend the money to fix all this stuff, that I'd do this swap that I started planning roughly 8 years prior, before I even owned the Jeep.
    The Steering Knuckles
    Of course, these are just the standard knuckles off of a WJ Grand Cherokee. These are what allows for the upgraded brakes and steering. However, the surface the wheel bearing mounts to is roughly 1/4" closer to vehicle center than the ZJ knuckles. This creates an issue with using factory ZJ axle shafts. The standard fix to this, is to weld a 1/4" spacer to that surface. Now, that creates an issue with the calipers, because they are now not centered over the rotor. So, the fix for that is to add 1/4" spacers to the caliper brackets to make all that line back up.

    To put it shortly, I did not want to deal with the spacers, and I didn't. I made up for the 1/4" in the axle shafts.

    The Axle Shafts
    Because I didn't want to have the spacer nightmare described above, I had to do something a bit different with the axle shafts. I haven't seen anyone else do it this way, and it did cause me a bit of trouble, but I think it was worth it in the end. A standard CV axle shaft on a solid axle, can be easily broken into 3 major parts: The inner axle shaft, the CV joint, and the CV boot. What I ended up using was the ZJ inner axle shaft, the WJ CV joint, and the WJ CV boot. I bought the WJ axle shaft assemblies from rock auto for $23ish, knocked them apart, and reassembled with the ZJ inner axle shaft. Then, I used brand new CV boot clamps *part number here* to reattach the boot.

    To get these apart, it *should* only take a few whacks from a rubber hammer, after you move the boot out of the way. With that being said, I had 2 axle shafts the would not separate with a sledge hammer. Not sure why, but it was a pretty major hang up.

    This part was almost entirely custom. The tie rod and drag link were made from 1.5"x.25" wall DOM tube, Ruffstuff threaded adjusters, and Ruffstuff hex tube adapters. The rod ends are Ruffstuff 7/8" LH rod ends using 1 standard 7/8" to 3/4" misalignment bushing, and 1 safety 7/8" to 3/4" misalignment bushing. I chose to use only LH threaded rod ends just to make the rod ends all the same. I used a pitman arm from an XJ because its offset is 3/4" less than a ZJs pitman arm, which makes up for some of the 2.5" difference between the WJ and ZJ drag link attachment point at the knuckle.

    Wheel Bearings, Ball Joints, Brakes
    All standard replacement WJ stuff. Nothing special here. I cheeped out on everything but the ball joints, due to how much work it is to get them out of the axle.

    Brake Hoses
    Out of all the reading I did for this swap, I didn't see many people mentioning needing different hoses. I suspect the reason for that is because most people doing this swap have lifted their Jeeps, and already have custom extended stainless lines. This was the biggest hang up of the entire project, and even after getting it "sorted out" I still don't like how it is. I couldn't find an off the shelf brake hose that would fit right, and ended up modifying one as a temporary solution. I will be revisiting this later. Along with that issue, the brake lines broke coming into the hoses, and we all know how fun that is to deal with.
    Overall, I am okay with how it all feels now that it is together. Steering feels very tight, and it is tracking good and straight. The brakes have always felt a bit soft to me on these Jeeps, and they feel a bit softer than before. That could be placebo effect, because I drove an early 00's Cummins truck all weekend, which has a rock hard pedal.

    I am getting what is known as "death wobble" in the Jeep community, which I believe can be attributed to the rudimentary tape measure alignment I did on it. Another potential cause can be some slop in the track bar, which I will be replacing this week.

    This is where I started, Friday and 10:00AMish
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    Had to burn out the ball joints, as usual.
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    And this is how it sits now.
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    I'll be adding more pictures and more information to this post in the near future.
    Last edited by DirtyDon6969; 06-08-2020, 12:00 AM.

  • #2
    Great work. I'm pretty surprised that these had such small brakes up front from the factory, but I guess that was pretty standard practice across all manufacturers back in those days.
    Originally posted by Dan
    My name is Edward