90 XJ Radius Arm to 3 Link

[wayne86]

Well, I signed up to do the Gray Rock ride in February and figured I needed to address my front axle problems before the trip. It is going to be close to a 10 hour drive for me and I want to make my rig last the weekend. I have a HD Dana44 HP front with RCVs and 5.13s on 38.5 boggers. I have broken 3 RCV shafts in about a year. Two of those breaks were not under what I would consider a punishing load. After watching a few videos of my jeep in action I noticed severe axle hop. I know I've had it, but seeing it in a video really made it stand out.
The upper links on the radius arm setup have a threaded heim on one end of them. I tried running those out a little to push the pinion up to keep it from trying to roll back. That didn't help. I put on new shocks...that didn't help. For clarification, and you will see in the pics, the radius arms are directly above the lower links and mount to the same ballistic coil bucket bracket.

Now on to the 3 link. I did some research and ordered up the parts I needed. I am doing a passenger side 3 link with a tower and inner frame bracket. I made a template to weld to the unibody so I can weld the bracket to it.

I think I will mount the bracket to where the bolt for the upper link is directly above the lower.

I orginally wanted to mount the 3 link tower on top of the axle tube to where it set perfectly perpendicular to the axle tube. This would make the 3rd link a few inches longer than the lowers. If I'm understanding this right that will keep the pinion pointed in the right direction at all points throughout the suspension cycle.
The reason I am posting this is to get some advice from you guys. Because the track bar is directly above the axle tube I can't mount my link tower where I wanted. Here is my option...

I feel like at this much of an angle that at droop the link is going to try to push the pinion down towards the ground. Am I right?
If so, can I get a new bracket that comes back enough to clear the track bar then back up to where it is straight again?
If I was keeping this axle I would go ahead and move the track bar forward with a new driver mount and a new mount on passenger side at the axle. For time's sake I don't want to do that because I would also have to relocate my hydro assist ram. I plan to put a 60 under it and will do all of that the right way, but for now I just want it to work for a few rides until I get the 60 located and parts on hand.
Any help and constructive criticism is greatly appreciated. This is my first try at any real fabrication. I have been getting the itch to do my own stuff and finally have a place and tools to get it done. Thanks guys!

 

[jwilson645]

Can we see a picture of your current set up? I built radius arms on my TJ but my uppers are bolted to the stock located axle mounts.

 

[LightBnDr]

I have run radius arm as well as 3 link on your unit body setup. Unfortunately your wheel hop won't go away or get drastically better between the 2 setups.
If you are dead set on a 3 link I would have used the OEM upper link mount on the long side tube then gusseted it for strength. That way it doesn't interfere with track bar mounting. Looks like you are past that? Already cut the upper mount off?

It's a pickle for sure because I think you've already started cuttin it up. You can run the upper link mount to the inner C on the long side. You can build a small tight truss over the center section to duplicate the OEM mount or use that OEM mount.

If you are goin to go tons soon I would not put too much time and fab into this update. You will have to do it all over again on your new axles.

Plus 3 links don't track equally during suspension cycles between the right and left side. The axle tends to roll under the rig on one side drooped and away on the other side drooped. The further away you get from centering the upper link mount the worse this becomes. So not ideal for high speed racing.

On my 3 link I ran my upper link mount where your new bracket is in the picture. Then I mounted my track bar to the same link mount.

On my radius arm I ran upper links to my inner C's then connected them to the lower links just like you did.

The 3 link flexed to the moon but had serious cycling issues because of geometry.

Both setups made no change to axle hop. Has almost everything to do with the new spring rate used to lift it high enough for larger tires. Adjustable rancho 9k's seem to help a small amount but nothin like you want.

Hope this helps man. Post up with you final design. Pics

 

[wayne86]

There was no factory upper link mount on the axle since this is an F-150 44 front. This is mostly a rock crawler. No high speed stuff unless I get on a gravel road or something going 50 mph. I can wheel it as is and pretty well be fine. I just want to try to make the wheel hop calm down so when I go on this big trip I feel a little better. I hate to do all the work and spend the extra money to move the track bar and ram. I will do all of that when I go tons, but I don't have time to get the tons located, built, and under the rig by the end of february. However, I can at least go ahead and mount my inner frame side bracket now and if I can't get the axle mount figured out or corrected it's no big deal. My coil springs are 6.5" springs. I will be putting some 4.5 or 5.5" springs in to see if that helps as well. The front sits a little high anyway.

What I'm thinking as far as the axle is mount something like this... I'll try to make some cardboard templates tonight. I found a local welding shop that can use their torchmate to make me new brackets. Then I can save the one I have for the 60.

 

[nhl_bullitt]

Cool looking trail rig. Will be even better after the 60 and new stance. Looking forward to the updates.

 

[wayne86]

Thanks nhl_bullitt. I've been following your build. Nice work. Any opinion on the bracket above? Or do I just need to bite the bullet and move the track bar?

 

[wayne86]

Looked at the track bar situation a little bit tonight. I may go ahead and push it forward a couple of inches. I think i can still do that and not make too many changes. Tonight's progress (not much) was a new inner frame, link mount. I'm taking it to a welding shop tomorrow morning to get cut out and bent. Hopefully they can get it done by New Year's so I can get it burned in.

 

[nhl_bullitt]

If you are able to move the tracbar mount forward, great. I wouldn't spend too much time on it if you are changing the axle in a month or so. I had my 3rd link axle mount tilted back on my prior 44 setup. It didnt react too odd or have severe wheelhop. My friend who had to utilize the radius arm mounts on a 79 f150 44 definitely had a problem with wheel hop. It would unload going up hills.

 

[jeeptj99]

there was a 3 link calculator on Pirate a while back that was helpful when i did mine have you used it?

 

[wayne86]

I haven't tried the 3 link calculator. I've seen stuff on the 4 link calculator. I really through the 3-link topic of the month on pirate. Basically what I gather is have the length of the upper slightly longer than the lower with somewhere around 8" of separation at the axle. Not sure if that's accurate. I'll do a search on pirate and see if I can find the 3-link calculator.
I took the cardboard template to a welding shop in Ft. Wayne today to get cut out and bent. Looks like somewhere between $80-100! Ouch. I need to find somebody else local that can do it cheaper. I was thinking $50 would have been close.

 

[jeeptj99]

I can't remember what mine was. I'll measure when I get back to where my jeep is. I don't think I had 8" at the axl .

 

[wayne86]

I don't know if it HAS to be that much seperation, but I remember reading that from, who I would consider a knowledgeable source. I'm checking for a 3 link calculator right now.

 

[wayne86]

Got the plate welded in and the link bracket in.

Tower is mocked up

The 3rd link may get into the exhaust. I'll put some pvc pipe in to cycle the suspension and see what hits and what fits.

Now I need to get an offset trackbar mount for the axle and new track bar mount for the unibody. Looks like a lot of hacking to make that all work.

 

[wayne86]

Mocked up the 3rd link with some PVC. I ordered some new panhard mounts from Barnes today. I have to get it out in front of the tower so it clears everything. Only three more weekends to work on it before our big ride.