XJ Front LCA mount Refab--staying with short arms......Ongoing

Here's the story:

'91 XJ, 4.0L + 2+years worth of wheeling with 33" Swamps and 35" MT/R's, the LCA mounts are starting to tear away from the cute little D30 axle. This seems to be a problem (IMHO). I hope to document how I fix it. Rather than weld on something that would probably work for a couple more years (how long will a unibody last), I want to improve my suspension geometry a little while doing it.

Here's the plan:

I bought (yeah, I know-make your own, but these are not that different than what I had envisioned and just as thick--10 minutes with a grinder and I'm in business) some 'tabs' (3/8" bastids ) from Mepco for some fabwork---they were like $7 or $11 apiece or something that will work great with the LCA spacing. I'll need to change the radius end a little, as they are built for a little larger axle tube (that might be telling me something right there about my venerable D30).
I'm planning on cutting off the factory LCA mounts, part of the rear of the spring 'mount' and rebuilding the rear of the spring 'mount' with the tabs from Mepco and a piece of 1/4" angle to reinforce the part that I cut off of the spring mount. But wait.....I've lost a shock mount..........front shocks...who needs those? I have some bar-pin-eliminators that I think I can mount up to the outside edge of the new LCA mount that will most likely work.

Possible/probable gains:

1)LCA arm angle will decrease to about that of a 2" lifted XJ--hopefully a nicer ride and less stress on various things like unibody's, axle brackets, etc.
2)I'll end up with near stock length LCA rather than the extended monsters that I have now (I can still use those--at least that's my intent) and adjust them in a ways
3)I don't think I'll have the 'down-and-back-to-go-up with the tire' problem that I've experienced when I'm climbing something really steep and need to have the front end flex--at least not as bad--because I won't have the extreme down angle on the LCA that I have now......
4)ground clearance under the axle. I've got axle tube and a pumpkin hanging as the lowest point. --I've got some pretty wicked looking gashes and edges on the stock brackets from where they hang.


Possible/probable issues:
1) If I do it wrong (i.e. not square), I might have an interesting time aligning the street-driven XJ.



Comments, suggestions and criticism gratefully accepted, then I can get on to the rear axle and hopefully to a welder before I get it back out to wheel.....

 

[I Lean]

Sounds pretty good, go for it!

The only problems I can foresee, will come from you altering the LCA's angle without addressing the UCA as well. Shouldn't be a huge deal, the rig should behave better than it does now--but you may get a touch more nosedive during braking, and junk like that.

 

[mbryson]

Originally posted by I Lean
Sounds pretty good, go for it!

The only problems I can foresee, will come from you altering the LCA's angle without addressing the UCA as well. Shouldn't be a huge deal, the rig should behave better than it does now--but you may get a touch more nosedive during braking, and junk like that.

I was (and am) a little concerned about that, but the angles will appear to be more 'matched' (at least in my mind) than they are currently. You have a little 'fab' experience. Is there anyway to guess what will happen without just doing it? The XJ (TJ, ZJ, WJ) front suspension seems designed at kind of odd angles anyway, at least in my non-engineering mind.

I'm really concerned about 'death-wobble' as I've had that before, and that's not a fun experience. I believe that could happen and the worst is that I'd have to change things back to stock, correct?

 

[I Lean]

I don't think death wobble should be a problem, at least not any more than it is now. In my somewhat-limited XJ-wobble experience, it's typically more related to caster and/or loose links/steering than improper geometry.

When you get right down to it, you've already messed up the factory geometry pretty substantially just by lifting it. Your roll axis became more angled away from horizontal, and your instant center moved way up from where it was off the showroom floor.

Raising the axle end of the LCA will tend to flatten out the roll axis, and lower the instant center (probably, but not necessarily), but it will give you less anti-dive. (could be good or bad)

If you've got some time to meet for a lunch sometime, or an evening, I'd be happy to go over some napkin-engineering with ya. (in case anyone's confused, that's sketches drawn on napkins....)

 

[mbryson]

Sounds good....maybe I'll stop by the shop one of these days with a paper towel roll and we'll go from there.

I was kind of thinking the same thoughts when I lifted it, but everything turned out OK.

 

[zukinrail]

Do you by chance have any pictures of your work? I jacked up my lower LCA mount on the front of my ZJ and need to do something with it. Need some ideas on how to go about taking care of the problem.

 

[mbryson]

I have some here.....they are kind of dark and I'm doing a remodel on Friday.......basicly the same idea, but slightly different. Where you attach the bolt for the LCA is CRITICAL for braking performance. I'm going to put the bolt center BELOW the axle centerline by about 1/2"-3/4" rather than at the axle centerline.

That'll still give me a net clearance increase below the axle tube over stock, but not anything like I have right now.

http://home.att.net/~mbryson/XJ-LCAmods.htm

That's probably as good of picture as I currently have. I have a better digital camera now and could document my changes a little better this time.

 

[mbryson]

Just an update to this thread. I have since removed the upper control arm from the passenger side and tied the upper control arm on the drivers side to the short arm on the drivers side. I also lowered the bracket on my axle on the drivers side to help control the axle from trying to roll under the rig on braking.

I now have some 'lift' on braking and lost some of my 'ride' characteristics, but it's not too bad. Better than the RE kit with the spacers.

 

[crimsonride]

I like that, I'm thinking of doing the same thing with mine. Any way you could get some more pics up? I like your creative thinking.
Be carefull with removing that arm, that places twice the stress on that single arm and four times the stress on the weld at the bottom of the bracket. Course, that's the one that's part of the pumpkin huh? Have you tried welding the tubes in to make sure they don't rotate? Just wondering how you've done it.
When I get the time I'll do the Vector Mechanics to find out how much stress that puts on the hardware. That's sorta the same thing RK does on their kits and they've been having issues with hardware. Maybe, it'll be necessary to upgrade to larger hardware.

p.s. a longer arm would reduce that 'lift' somewhat, but that's not in your plans.

 

[mbryson]

I like that, I'm thinking of doing the same thing with mine. Any way you could get some more pics up? I like your creative thinking.
Be carefull with removing that arm, that places twice the stress on that single arm and four times the stress on the weld at the bottom of the bracket. Course, that's the one that's part of the pumpkin huh? Have you tried welding the tubes in to make sure they don't rotate? Just wondering how you've done it.
When I get the time I'll do the Vector Mechanics to find out how much stress that puts on the hardware. That's sorta the same thing RK does on their kits and they've been having issues with hardware. Maybe, it'll be necessary to upgrade to larger hardware.

p.s. a longer arm would reduce that 'lift' somewhat, but that's not in your plans.

You're welcome to take a spin in mine before doing similar to yours. In fact, I'd recommend that. It's not bad, but kind of interesting and I'd tell you what I'd do a little differently. It could make a world of difference. I'm not sure when I'll get back to SLC, but it shouldn't be too long. I'm planning on being over there Feb. 14 weekend if you wanted to check things out.

I think a longer arm would solve a lot of problems. The lift is not a bad situation and isn't that significant--just odd. I've got a 3/4" heim on the one end (had one laying around) and bracket to the cast piece on the housing. I'm not worried about the arm. It's pretty stout, but I do inspect everything all the time. I'll have my wife bring over my dig camera and take some updated pics.

I haven't welded the tubes in but the lower control arm bracket welds to the housing and to the axle tube ('cuz I suck). So the drivers side is 'welded' but the passenger is not.

Which bracket are you speaking of when you say........"and four times the stress on the weld at the bottom of the bracket. "? The axle bracket is 3/8" steel and welded quite securely despite my poor welding 'skills'. The "frame" end bracket is definitely suspect and has REGULAR inspection.

My avatar picture kind of shows my current problem......take a good look at that and tell me what you don't like.......

 

[crimsonride]

My avatar picture kind of shows my current problem......take a good look at that and tell me what you don't like.......

Actually, I like it all, seems like thought it through. You get plenty of flex, lots of clearance and it's plenty strong.
I was thinking of the passenger side bracket weld, only you had the driverside which is cast into the housing so nothing to worry about there. I was just pointing out that if it hadn't been cast the weld would have been stressed greatly. The length of the bracket acts as a moment to the force applied through the arm....blah, blah, blah....nevermind.
I'd really like to see it. Give me a call when you come up here, or I'll swing by on my next trip to moab. I'll pm ya my number.
Just wondering, how much lift does it have?

 

[mbryson]

Actually, I like it all, seems like thought it through. You get plenty of flex, lots of clearance and it's plenty strong.
I was thinking of the passenger side bracket weld, only you had the driverside which is cast into the housing so nothing to worry about there. I was just pointing out that if it hadn't been cast the weld would have been stressed greatly. The length of the bracket acts as a moment to the force applied through the arm....blah, blah, blah....nevermind.
I'd really like to see it. Give me a call when you come up here, or I'll swing by on my next trip to moab. I'll pm ya my number.
Just wondering, how much lift does it have?

It actually flexes too much. Kind of scary, to be honest. I keep wondering when it will just roll underneath my Jeep and take out the driveline and transfer case. For that reason alone, I will strap it OR use a longer arm (that would kill at least a little of the 'lift' problems).

You'd be going a little out of your way on your trip to Moab.....I'm in Roosevelt.