Modified JK rear suspension brackets: Did I screw up or should I continue?

[Rob50lx]

My intentions were to raise the rear axle-side control arm brackets to mimic Metalcloak's DB3 drop down brackets. Purpose was to minimize rear steer while gaining ground clearance. I want to continue using the MC control arms while mainlining a stock-like rear suspension.

I was able to keep the upper control arm frame mounts stock while raising the upper axle-side brackets 3". I thought things were looking good until I realized the brackets weren't deep enough and caused a bind when flexing the rubber based joints. I was able to clearance the brackets which allowed me to articulate the axle in a simple up and down motion but still had serious bind when trying to simulate full stuff and droop on opposing sides. With the current new upper locations and the untouched lower mounts, I'm at 12.5" of joint separation on the axle. I believe I need to get back to the 9" of joint sepration by raising the lower axle-side mount by 3" which will require new lower frame mounts to maintain the stock lower control arm length.

Should I go back to stock brackets or should I continue with raising the lower axle-side brackets 3" and relocating the lower frame-side mounts using the Artec lower frame brackets?


Proposed new lower frame brackets

Where I'm at now but with the upper control arm bracket fully welded

Rough idea of replacement lower control arm mount

 

[wvracer821]

have you considered going to a 3 link out back like the rockkrawler kit? a parallel 4 link will always have some kind of bind

 

[thedirtman]

A 3 link will bind as well since it still uses a track bar. The RK 3 link has actually been cracking the frame where the upper arm mount is welded too because of the bind.

OP I would go even higher with the lower link if you have proper separation. The problem will be that your arms will likely be too long because the mounting hole will be pushed forward as you rotate it around the tube. I would ditch that rear track bar and build a straight one and make it as long as you can by locating that track bare further left. What are you doing for a rear shock mount?

 

[Rob50lx]

I will have to get some more pictures. The stock mounts with MC arms allowed me to almost max the 13" of shock travel but I was binding up on the fuel tank skid plate do to the increased roll steer at 3.5" of lift. I was hoping to minimize the gas tank skid contact by leveling the arms by raising them on the axle-side by 3" I have raised the axle-side track bar bracket 6" and I was thinking of lowering the frame-side track bar bracket possibly 1" after I complete the control arm mounts.

My plan with the lower mount is to get back to 9" of joint separation which will put the control arm bolt hole right at the bottom of the axle tube. Since this will move the axle mount about 2" forward from the stock position, I will use the Artec mounts to relocate the frame-side lower mount 2" forward.

I am happy staying with coil springs and 13" travel 6Pak shocks for my situation. Without altering the lower mounts yet, I have increased the joint separation from the stock 9" to 12". This has created a severe bind where I cant cycle one side of the suspension without the other side following, When I remove 1 upper link from the axle-side mount I can get full articulation and the control arm moves about 1" away from the mounting hole. This is what I need to take a picture of to show how I can't articulate the suspension.

I have raised the shock mount as high as possible on the stock lower control arm mount. I will box the upper part of the mount once I cut the lower control arm mount off.

 

[Rob50lx]

I can't articulate my rear axle without disconnecting one of the control arms and creating a 3 link. I'm hoping it is only because I am half way through the project. I'm hoping that by raising the lower control arm mount on the axle until I'm back to 9" of joint separation will fix this problem. I believe I need to stay close to 9" because of the 25% of tire diameter rule. I'm already running 37" Coopers and would like to eventually upgrade to a true 37-38" tire and I would prefer to stay with the rubber joints.

Since the lower axle bracket will be pushed forward which will require me to redo the lower frame mount, I was wondering if I should lengthen the lower control arm by 2" from 20.5" to 22.5"? I'm thinking only 2" to maintain the approximate 80% ratio of upper to lower control arm length. The upper is 18.5" long. Is lengthening the lowers only 2" worth the trouble?


So here are some pictures of my problem:

 

[thedirtman]

You have to remember the metal cloak joints are always in bind during articulation. The center section is pinched in the bracket and the center section has to flex around. You may not have enough weight on it to get the joints to full flex without the wheel on it. I would not worry about lengthening the lower arm as the rule of 80% is a minimum and the differences in length determines how your pinion will react during articulation. I would also think about a lower shock mount that is going to push that mount out farther for better clearance to the big 6-pack body. Maybe something like these. https://www.ruffstuffspecialties.com/SHKBASH.html

 

[Rob50lx]

I'm making some slow progress. I've only done the driver's side as I need to drop the gas tank to weld on the passenger's side frame. I'm wondering if I can strengthen the shock mounts or if I should start with fresh new mounts. I'll wait and see after I complete the other side mock-up.
I lost 1" of ground clearance with the new lower control arm mount but I have gained 3" of additional ground clearance on the axle side. My mounts were already cut level to the control arm, so I'm guessing that I gained 6" at the axle compared to stock untrimmed mounts.

I'm using Synergy replacement rear frame lower control arm mounts as they seemed to work well for my situation. The control arm is moved forward about 3" due to the mount on the axle. The notch on the control arm mount is supposed to line up with the rear part of the body mount.

I will also need to alter the parking brake cable mount above the rear control arm mount.

6.5" of joint separation at the frame compared to 6" stock.
9.5" of joint separation at the axle compared to 9" stock

 

[thedirtman]

Can you widen out the lower axle link mounts? You may just want to add a plate to the bottom of the shock mount, since you are running standard coils you don't have to go crazy on the shock mounts.

 

[Rob50lx]

Can you widen out the lower axle link mounts? You may just want to add a plate to the bottom of the shock mount, since you are running standard coils you don't have to go crazy on the shock mounts.

What would I gain by moving the lower mount outward? I could do it if I use the Artec mounts that I have posted in the first post. I'm already maxing out the articulation of the joints, would moving them mounts outward affects the articulation.

I'm still considering your idea of changing the shock mounts if it will allow me to fit a longer track bar. I will work on that after I figure the the control arm mounts.

 

[christensent]

A 3 link will bind as well since it still uses a track bar. The RK 3 link has actually been cracking the frame where the upper arm mount is welded too because of the bind.

OP I would go even higher with the lower link if you have proper separation. The problem will be that your arms will likely be too long because the mounting hole will be pushed forward as you rotate it around the tube. I would ditch that rear track bar and build a straight one and make it as long as you can by locating that track bare further left. What are you doing for a rear shock mount?

A 3-link should never be in a bind, unless it's designed wrong with rod-ends that have insufficient mis-alignment etc. which is different. I don't think it's possible to make a suspension that goes into bind with only 4 standard links (by standard link, I mean two rod ends one on each end, not a wishbone etc.). You'd need 5 links to get it into a bind.

My rear 3-link definitely had zero bind, in the shop I could go full articulation, full stuff, full extension all with zero bind. Still cracked the 3-link mount, the crack is just from suspension force not bind.

 

[thedirtman]

What would I gain by moving the lower mount outward? I could do it if I use the Artec mounts that I have posted in the first post. I'm already maxing out the articulation of the joints, would moving them mounts outward affects the articulation.

I'm still considering your idea of changing the shock mounts if it will allow me to fit a longer track bar. I will work on that after I figure the the control arm mounts.

It adds stability in cornering.

 

[Rob50lx]

I'm making progress after raising the lower axle bracket up to the axle centerline. It also looks like I will move the mounts 1" outward just based on their relaxed position in the mounts. I now have full articulation without any bind. My only concern is with axle wrap as now I'm at 8.5" of joint separation at the axle and the joints are now at axle centerline and 8.5" above. Will that play a major role in axle wrap?

Now that I centered the axle in the wheel well during full articulation I need to do something about my upper control arms. They are too short now. I don't have the means to tap my own and I'm looking at different options; lengthen MC arms, buy MC rear lower arms for upper position, New straight links with heim joints, New straight links with 10 degree MC joints, etc.

 

[thedirtman]

25% of tire height is the rule of thumb. I doubt you will notice any axle wrap. You will feel some squish of the duro-joints.

 

[Rob50lx]

The learning curve continues. I now need a set of Front LCA since that is what I'm using in the rear for LCA. I think I would like to make a set of straight arms using either the Metalcloak Duraflex joints or possibly Barnes Enduro Joints. I like that MC joints return to center but is that even needed with straight arms if they are indexed correctly? How are Enduro joints holding up?

 

[thedirtman]

Enduro are almost an exact copy of the Johnny going, you can even swap rebuild kits in them For bind free use the Enduro or for more comfort use the M
Duroflex joint.

IF you change your mind down the road you can also put a Duroflex joint center in the Enduro housing.

 

[Rob50lx]

Finally got it back on the road. It drives great and at least doesn't feel worse than stock. It's hard to tell if I made any improvements with only driving it on the road and also the fact that I haven't driven it for almost 3 months.

It ended up with about a 2" stretch. It is currently using stock front LCA for the rear LCA. I just got some builder joints in the mail so I'm about to order some aluminum links or build DOM links if I can't find anyone that can tap 1.25-12 to 3.5" depth.

I'm researching high angle driveshafts as the current 1350 shaft can't handle the 13" travel shocks at full droop and I just picked up a pair of 15" shocks that I could use if I can find a good enough driveshaft. The current 1350 shaft clears the gas tank during full articulation but I'm not sure if anything bigger will without offsetting the axle.

 

[Gregj50!!!!!]

Good information... keep the updates coming when you start your link project.....

 

[thedirtman]

A 1410 shaft shold do the trick for you. You could also install a limit strap at the differential that would protect the driveshaft and allow each wheel to fully stuff/droop when crawling. I would run a straight track bar with that rear raised bracket. Any issues with that bend hitting the bottom of the storage area?

 

[Rob50lx]

So I finished the project and would rate it a success. It has been so long that I drove and wheeled it that I can't say I made a drastic improvement but I feel confident that I didn't make it any worse than a factory style 3.5" lift.

Setting up a short arm 5 link requires a lot of trial and error to eliminate link bind. Anything more than 8.5" of joint separation at the axle caused serious bind and loss of articulation. I have a friend that is using the MetalCloak DB3 drop brackets and factory axle mounts with heim joints instead of rubber joints and his axle is bound up at the slightest amount of articulation. Had I known this in the beginning I might have skipped all this crap and went with a 3-link. I am debating if I should borrow some used up 1.25" heims or find cheap ones and install them into my suspension to see how bad my bind is. I guess I will watch my Duraflex joints and see if I have caused accelerated wear on them.

1. I gained 3"+ ground clearance at the axle compared to before and probably 6" compared to a complete stock rear axle brackets.
2. I only lost about 1" of clearance at the frame LCA mount.
3. I would still call this a regular arm or mid arm 5 link suspension. The new rear LCA is 22.5" while the UCA is 20.5" and I added about 2" rear stretch. Factory lengths are: lower 19.75" and upper 17.5"
4. I get less roll steer. The 1350 driveshaft no longer contacts the gas tank skid but some of that is from more cutting.
5. I get a full 13" of shock travel and I will eventually upgrade to 15" rear shocks if I can get a driveshaft that can work at those angles and I can find a long enough coil spring.


Final things to wrap up this project:
1. Add center mounted limit strap
2. Adjust bump stops
3. Redo or strengthen lower shock mount with skid plate to protect 6Pak shocks
4. Drop down bracket or longer brake lines
5. Add some kind of spring loaded cable hanger to manage the parking brake cables after being relocated for more droop

 

[Mattygwheeler]

No rear sway bar?

 

[Rob50lx]

No rear sway bar?

Not anymore.

When it was a regular 3.5" lift I had the rear on for a while. That is when I noticed that it was limiting my articulation. When I removed it, I gained a few more inches of travel but then the driveshaft started contacting my gas tank skid. That helped inspire me to do this project. I didn't like the bolt on solutions that lost 3" of ground clearance and I didn't really want a bolt on long arm kit either.