I need to three link the front and rig up a crawler box and I can call it quits on the Avocado 
So, is the center mount on the stock crossmember?
So, is the center mount on the stock crossmember?
3-link ala Action Jackson (1 Viewer)
- Thread starter Discyota
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Still tinkering with loose ends but thanks for the comments. The pics aren't very clear and Rick has better ones I haven't seen yet.
The cross member was an IPOR blem. Attached vertically on each outside edge are 8" x 8" x 0.25" plates that capture the four holes in the vertical face of the frame facing out. On the PS these four already have 8-mm x 1.25 captured nuts. On the DS only one has the captured nuts. The other three have rivnuts rated to grade-8 hardware. Each plate then has a gusset running from the top edge of the vertical plate down to the top of the bracket. The brackets are 0.25" steel. Each bracket is welded to the cross member and the vertical plate. One of the cross member bolts goes through the bottom of the bracket, through the crossmember and into the bottom of the frame to the captured nut. Used a hole saw to create access through the bracket large enough for the socket to fit through it to ease install/removal. That whole cross member really became the center piece for this with so much integrated in it. It is pretty well boxed around the frame rails now with the forces spread out really well and fully 0.25" and 0.375" steel plate gusseted everywhere. The lower frame mount brackets are at around 10-degrees from the axis of the frame rails there since welding flat plate directly to the frame presents two problems. One, putting flat plate on each side of the frame rail doesn't create a bracket width great enough to hold the joint, you'd have to space it out with an additional 0.25" plate or maybe a little more or bend your plate out that far. Second, the frame rails are curving in at that point and using flat plate would have the bracket aiming in while the brackets on the axle would be off laterally to those. This pre-loads the joints, not likely a big issue with Johnny Joints or heims but not good for rubber or poly ones, so it was decided to deal with that in the build.
The cross member was an IPOR blem. Attached vertically on each outside edge are 8" x 8" x 0.25" plates that capture the four holes in the vertical face of the frame facing out. On the PS these four already have 8-mm x 1.25 captured nuts. On the DS only one has the captured nuts. The other three have rivnuts rated to grade-8 hardware. Each plate then has a gusset running from the top edge of the vertical plate down to the top of the bracket. The brackets are 0.25" steel. Each bracket is welded to the cross member and the vertical plate. One of the cross member bolts goes through the bottom of the bracket, through the crossmember and into the bottom of the frame to the captured nut. Used a hole saw to create access through the bracket large enough for the socket to fit through it to ease install/removal. That whole cross member really became the center piece for this with so much integrated in it. It is pretty well boxed around the frame rails now with the forces spread out really well and fully 0.25" and 0.375" steel plate gusseted everywhere. The lower frame mount brackets are at around 10-degrees from the axis of the frame rails there since welding flat plate directly to the frame presents two problems. One, putting flat plate on each side of the frame rail doesn't create a bracket width great enough to hold the joint, you'd have to space it out with an additional 0.25" plate or maybe a little more or bend your plate out that far. Second, the frame rails are curving in at that point and using flat plate would have the bracket aiming in while the brackets on the axle would be off laterally to those. This pre-loads the joints, not likely a big issue with Johnny Joints or heims but not good for rubber or poly ones, so it was decided to deal with that in the build.
the lower arm frame brackets do come off with the cross member - only 20 bolts if you include the two for the Johnny Joints
lowers are 34", upper is 30"
Mike,
So with this kit can I run 33's?
-Ammo
So with this kit can I run 33's?
-Ammo
Some day we'll be able to buy a skid plate/cross member/3 link kit like the long arm kits for TJ's. I really like your mostly bolt on bracket design. Somebody should be working on selling a skid plate/cross member/bracket kit. The 80 market is growing all the time with these mall cruisers getting traded in.
Did you go with rubber bushings on one end of the links? Or Johnny Joints at both ends of all the links? Any noticeable NVH changes?
What would you have to change for a 4 inch lift? I keep thinking the tower on the diff would have to be lowered for a 4 inch, due to oil pan and motor mount clearance. I'd probably need to lower the lower links too, and lose some ground clearance, to keep the same vertical separation for axle wrap.
Any mods to the steering for all this flex?
How much did you increase the wheel base?
Did you go with rubber bushings on one end of the links? Or Johnny Joints at both ends of all the links? Any noticeable NVH changes?
What would you have to change for a 4 inch lift? I keep thinking the tower on the diff would have to be lowered for a 4 inch, due to oil pan and motor mount clearance. I'd probably need to lower the lower links too, and lose some ground clearance, to keep the same vertical separation for axle wrap.
Any mods to the steering for all this flex?
How much did you increase the wheel base?
Very interesting...
Carl @ Outback Offroad already offers this. The problem is it isn't really cheap or easy. There's over $1500 dollars just in materials there if you include the front springs and shocks and that doesn't include the substantial amount of time and shop resources I had access to. Add to this a very limited number of potential customers and if you charged $3K to do this you'd go bankrupt.
I used Johnny Joints at all six locations. Five fixed and the upper frame one threaded for caster adjustment. I don't see any benefit from rubber bushings in this application and with the truck modified as it is. Not sure what NVH is...?
It is very surprising to see where the tower fits. The oil pan isn't an issue. The front edge of the PS motor mount and the back edge of the coolant elbow are.
High steer is in the works.
Not sure. Basically aimed to have a 37-40" tire centered in the front wheel wells when stuffed. Those pics are of new 37/12.50R17 BFG AT's.
yes, but you can't run a front driveshaft as seen in my pics or you'll get horrible driveline vibs. there's really no solution to this but since I have a CDL switch and a rear locker I have TRUE two-wheel drive which suits the "trails" in SoCal just fine (you know them...Sunset, Rodeo, Santa Monica, Wilshire)
Sorry, NVH is Noise Vibration and Harshness. I was just wondering about the ride. Any noticeable changes in forces or vibrations transmitted to the cab? I've been trying to design a 3 link for mine, and I keep wondering if I should have rubber bushings at one end to absorb vibes. I'd rather not, but not sure if it would be an issue.
Did you use any kind of CAD (or suspension program) to setup the link geometry? I've been trying to use a constrained (stick figure) sketch on CAD to simulate the movement of the links, and resulting drive shaft angles, caster, etc. From dragging the sketches around, I noticed that it would be really easy to screw up the placement of the links so that the axle would rotate a lot through the suspension travel. Its a little hard to find a geometry to be confident in.
Would you mind giving your mounting points and link angles for reference? Might be able to estimate it from the pics.
Did I read it right that the lowers are triangulated at 10 degrees (both sides)?
Did you use any kind of CAD (or suspension program) to setup the link geometry? I've been trying to use a constrained (stick figure) sketch on CAD to simulate the movement of the links, and resulting drive shaft angles, caster, etc. From dragging the sketches around, I noticed that it would be really easy to screw up the placement of the links so that the axle would rotate a lot through the suspension travel. Its a little hard to find a geometry to be confident in.
Would you mind giving your mounting points and link angles for reference? Might be able to estimate it from the pics.
Did I read it right that the lowers are triangulated at 10 degrees (both sides)?
Very nice, glad to see something different in the 80s section.
I have a CDL switch and a rear locker I have TRUE two-wheel drive which suits the "trails" in SoCal just fine (you know them...Sunset, Rodeo, Santa Monica, Wilshire)
Family leaves for the east coast and your hanging out on "Sunset" oh man.....
Be back in Aug.....
-Ammo
Don't worry about NVH with Johnny Joints. They are no worse than poly bushings, you'd have no real issue with them on a unibody Jeep. On an 80 you have the additional isolation of body mounts, so you don't want the rubber. It will just add slop to the system, and a 3-link has no inherent bind so it is an opportunity to get rid of bushing deflection. If your bushings can deflect to handle flex, they can deflect in every other situation as well. I'm not sure I've seen anybody do a 3-link and leave rubber on one end - the Jeep long arm kits keep rubber on one end because they are still four link and need the deflection.
Yeah, that makes sense. I haven't seen any 3 links with rubber bushings on one end, either.
any more updates on this project? steering? road manners? highsteer? flexed out?
Road manners with both swaybars off was a bit too squirrelly for Los Angeles freeways so I was able to retrofit the front sway bar on and re-intalled the rear sway bar for highway driving. With the front sway bar on though it really can't be flexed much at all before the front driveshaft hits the sway bar.
I just drove it this way ~300 miles each way to run the Dusy-Ershim and then completely removed both swaybars at the trailhead. This was with the 37" Toyo M/T's. Did ok on the way up @ 40 psi but on the advice of a friend we put the tires up to 60 psi on the way back and it was better.
I took it in to an alignment shop on Weds to finally check everything out and the caster was at 6-deg (amazing since we had "guessed" at it while installing the 3-link), the camber was still in factory spec, and the toe-in was actually toed out. Had that corrected to be a wee bit more toe-in than factory and now it drives pretty good for a truck set up like it is. The good thing in my opinion, was that it could all be in factory spec with very little effort.
High-steer will happen as soon as possible. The one thing that seemed to happen on the Dusy trip is that the steep angle on the front panhard puts a lot of stress on it when repeatedly flexing out. I had both the upper front panhard bolt and lower one back out and nearly lost both at different times. When I finally got off the trail I noticed that the upper front panhard frame mount had cracked completely around the outside frame area.
The front will extend and compress the Bilstein 7100 14" shocks their complete cycle. I've extended the cone bumpstops to protect the shock and to re-center the springs. I've only got the springs retained at the bottoms for now and am seeing how that works. I need to put on limiting straps to keep the shocks from over-extending.
The actual 3-link portion worked flawlessly and has no interference, clearance, etc issues. I did hit the tie-rod a few times since it is now the lowest thing on the back side of the axle but it is the 0.25" DOM with GM 1-ton TRE's and it seems to be unharmed other than some scratches. That will change with the high-steer though. It will have hydro-assist too.
Not really any pics showing the flex until the ones from the Dusy trip get circulated.
Dusy thread with some pics (https://forum.ih8mud.com/showthread.php?t=171560)
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of what?
