[shelljeep]

Some of this was covered in my Jeep Surgery thread, but I'll be going into further detail in this thread.
This wishbone suspension design has been around for a long time and has a bad rep because of the ghettofab versions that are out there.
I saw it as a simple, strong way to kill any axle wrap I had in the rear of my CJ7, and set out to do it as cleanly as I could.

This is the CJ7 after I finished. Running 37's at stock height(when measured from axletube to bottom of frame rail). 108" wheelbase.

Here are a couple pics of the joint I used. It's a custom piece that a buddy of mine made a short production run of. There are no more to be had. Made from 3" 4130 round stock, 1" shank.

This is what I used to mount it to the crossmember, 1/2" steel. Takes a long damn time to holesaw through 1/2" steel. Was welded on both sides.

For the crossmember, I'd originally intended to use 2x4x.120 wall tubing with a couple of doubler plates, but I went with 2x4x.250 wall tubing instead. Simpler, and less to worry about bending down the road. This rig's gonna end up with 44's or better.
Another thing I could have done differently was the frame windows. I probably should have just cut windows in the inside of the framerails, instead of all the way through. Could have doubler-plated the inner windows also. I may add some 3/16" flatbar to strap the area where the framerail's thin around the top and bottom of the x-member. Here's a shot of the crossmember being sleeved, and the windows I cut in the frame to slide it through.

Here's a shot of the x-member slid through the frame, and a shot from the opposite side after it's been welded, showing the 2x4x.120 wall gussets I used to brace it on each side. You can't see it at this stage, but there is also a brace that is directly behind where the joint attaches, it bolts the crossmember to the flat skidplate. Getting the D300 in there is a bitch.

 

[shelljeep]

I knew I was going to mount the wishbone to the top of the axletube, like an SOA rig, and I would need some clearance for uptravel if I was goona stay as low as I wanted. Something had to go. So, here's some shots of the frame being chopped, I removed about 57" worth. The icing on the cake was a 70 year old neighbor coming up to me in the middle of it to ask if he could pick some of my pecans that were laying in my yard. He saw my sawzall and was like wtf are you doing?! I had never even met the guy before. I laughed. And then tried to explain, eventually he went back to the pecans and let me finish. Funny. Nice old man. Liked my nuts.

This subframe is built out of 1.75 .120 wall HREW. Probably the most difficult piece to bend in my entire chassis. One piece. It uses 2 of the stock body mount locations to support the tub. It was eventually tied into the cage also.

The subframe was actually welded to the crossmember(as much as I could get to, anyway), than this piece was slid down to box the end of the frame rail and was welded in place.

This gusset is built out of 2x4x.120 wall tubing.

 

[XJ_ranger]

wow

 

[shelljeep]

The wishbone itself is built out of 2x3x.188 wall tubing. Here's a shot of the front end where it attaches to the joint, and a shot of the bracing I put on the miters.

Here's an overall shot, and a shot of it installed during mockup. I don't even want to think of how heavy this damn thing is, and it's lighter than most I've seen.

This will give you an idea of how tight it is for my Dana 300. That is the rear yoke above the crossmember. I added a torque bar to keep it still, and raised the tranny mount 1/2" to help keep it out of the crossmember.

I'm pretty pleased with how well the CV ball and the joint lined up on the vertical plane.

The panhard is 33.5" long and has about a 10* slope to it. It's built out of 1" solid rod and uses 3/4" heims. You can see a short limiting strap in there also. More on this later.

 

[shelljeep]

So how does it work?

It's late, I'm gonna keep it short.
I wish I'd gone with a 4-link instead. Ain't that a bitch?

I said it best earlier today:

The one-link(wisbone w/panhard) works. It killed all axle wrap, which was my main goal. It would offer unlimited flex if you're into that. I have mine limited so that I can hang a tire in the air when I need to.

There are some things I don't like about it though.
#1 problem- HUGE amounts of A/S with this design.
#2 problem- STEEP rearward slant to roll axis.
#3 problem- No way to tweak the design to make it appreciably better

I'm running a wishbone that has it's pivot point(instant/constant center) almost 4 freakin' feet from the centerline of my axletube, and there is only 6" of difference between the height of the ball(22"), and the centerline of the axletube(16"). It still calcs at a little over 200% A/S.
The axle is stretched to where it's almost even with rear of the tub, and I'm sitting at stock height when you measure the distance between axletube and frame. Low, and long. I think my COG is around 30"
Still, even crawling at an idle, I could hump a rock like nobody's business before I installed a tight center limiting strap.

The tight center limit strap has it's own set of downsides.
The tight center limit strap works to kill the jacking, but it's a bandaid.
When you're on the onion and the strap is stretched tight, it's nice and planted. But when your suspension compresses and the the strap gets those few inches of slack, still under throttle, it still slams that strap tight and gives you some mini-hump.
This ain't good for the mounts, chassis, or housing. And it doesn't feel good from the driver's seat, even on the high speed runs between trails.

I could get used to it, and I'm not gonna rush right out and swap rear suspensions, but when I install my D70U next year, it's gonna be 4 link, or a double wishbone.
More expensive, but lighter, stronger, and I can tune it to do what I want through design.

 

[Erik D_lux]

Nice work. I really like the frame/tube gusset.

 

[EBSTEVE]

when I first looked at it and saw the x-member I thought you were a crack head, then when I got a bit further and saw that you were ending the frame there it made sense.
Looks good and it's too bad that you went to all that work and wish you would have gone a different rout. It's hard to tell from the picture but to me it looks like you could rework it to be a three link by adding outer links and removing the track bar.

 

[shelljeep]

Thanks Erik.
Steve, that's true. I can still easily do a 3 or a 4-link. Could build off the work that's already done, would just need to fab brackets and make links. And I will one day.
I thought about using a different method to locate the axle laterally, like you mentioned, and that could change some of the characteristics, but not the antisquat.

 

[mj]

what would your AS numbers be if you moved the pivot forward and down under the transcase?
a 4' IC is not really that long, but it is far longer then a stock ford radius arm design

 

[shelljeep]

I've only got 20" clearance at the skidplate. I'm sure moving the pivot under there would help the A/S%, I just can't give up that much clearance.

 

[deepmud]

FWIW, I have seen more than one 4 link end up with a tight limit strap.

I also think a strap, perhaps linked with a bushing, would be easier to live with than a limit chain. At least until you get a 4 link built.

 

[TheNerple]

What motivates people to build a non adjustable suspension and trust it all to a single point? Especially considering the fact that antisquat/antidive figures are unchangeable? I'm actually curious because it seemed like one person posted this suspension which totally looked booty fabbed and quite a few others have followed. So what drove you to build such a suspension? It looks cleaner than most, but you're still stuck with all the negatives.

 

[shelljeep]

It's simple, and I thought I wouldn't mind the tight limiting strap as much as I do.
It still works, and it's strong and cheap.

I don't hate it so much that I'm gonna run out and cut it off the heep, I'm gonna wheel the piss out of it. And it climbs like a billygoat compared to leafs nnow that I installed the tight center limit strap, but it will get swapped for a 4 link when I go 1-ton.

I knew some monkeys would fling shit when I started this thread, but I felt like people should be aware of the flaws it will have, no matter how cleanly it's built.

 

[TheNerple]

The purpose of the post was to understand why you did what you did, not to "fling shit" so I hope you don't misunderstand. Because of antisquat forces through your links, that 1" shank sees a lot of stress, no doubt compounded by the fact that you're running a limiting strap at the axle. I'm actually glad you posted this cause I think a lot of times people see something different and copy it without thinking through the negatives. I find it interesting that you say this setup is simple because to me it looks to be more of a PITA than doing a "simple" 3 or 4 link. Anyway thanks for putting this post up, hopefully it will save some headaches for others. Quality tech.
Your AS numbers are going to vary mostly by the seperation of the links at the chassi so simply moving the pivot down lower still leaves you with the same seperation.
I don't know what you moslty do, but if you're looking for stability I highly recommend a more traditional 3 link but with your panhard at the axle mounted higher. 4 link will give you perhaps better handling for jumping and such.

 

[deepmud]

the folks who like it, like it. Some are booty fab, and they still like it. Like I said, there's more than a few 4 links with the back end winched tight, adjustable or not. Scorpions work ok - alright Soni ended up with an "air spring limit strap" but it's an example of a one-link that has been running around awhile and working well enough.

 

[born loser]

this setup has also been run for many many years by top competitors who happen to be engineers. The forces on the single joint are far less than the forces on the ends of the links on a 4 link.

 

[Ramrock]

Looks like one of the better build ones ive seen. You spent some time on the ball and socket. i would have bought a graderball set up probly three times stronger. No biggy looks good.
How did you mount it to the axle. less see some pics. What does it lift alot On set down then you gas on it. this is the only thing i cant figure out on these set ups.

 

[Ramrock]

Should have made your panhard bar flat. You'll have less rear steer. With it flat. At a angle it get longer and shoeter as you travel it.

 

[shelljeep]

I find it interesting that you say this setup is simple because to me it looks to be more of a PITA than doing a "simple" 3 or 4 link. Anyway thanks for putting this post up, hopefully it will save some headaches for others. Quality tech.
Your AS numbers are going to vary mostly by the seperation of the links at the chassi so simply moving the pivot down lower still leaves you with the same seperation.

I guess I consider it simple because there isn't much need to do the computations involved in tuning a 4 link design. It won't change much anyway. And it's basically just 2 pieces, wishbone and panhard. You are right that it shares all the other work involved in a 3 or 4-link suspension, as in building crossmembers, brackets, etc.
You mention A/S being affected by the vertical seperation of the links at the chassis, I agree. What you are doing is "aiming" your instant center at a certain spot in relation to your COG height. This pivot point is my instant center, actually my constant center because it doesn't change as the axle moves. So moving it will definitely affect the A/S %.
Not saying I know alot now, but fer sure, I knew a lot less about suspension design when I committed to this setup.
That was an excellent point about the limiting strap increasing the load on the shank. Hadn't thought of it, but I still think it's strong enough. Especially since it won't reach a point where it binds.

 

[carwash]

yes, the attention to detail is nice.