Rear LCA experiences over the years

[pass1over]

In your case, I would suspect shock mounts at either top or bottom, perhaps even swaybar mounts.

Shock mount top hardware and bushings are all new. Bottom bolt is new, oversized, snug in the bracket and tight.
Sway bar bushings are poly, hardware is oversized and has lock nuts.

 

[Pentalab]

Ex-wife?

A 350 lb woman is what I would call...'full figured'.

 

[Norm Peterson]

put new bolts in the front of the LCAs, where it attached to chassis. Don't think it helped at all, noises are still there.
However, yesterday otw home, I had about 350lbs in my trunk, and going down my dirt pothole filled road driveway, most of the noises and sounds were gone. So extra weight/compression on the rear of my car almost silenced it. Does this point to anything specific I should look at?

Loose or bad bump stops is all I can come up with. I can't see lateral axle migration under the heavy load being enough to be a significant contribution to either centering the stops on the chassis-side pads or moving them off the pads completely.

Chances are you were riding on the rear bump stops most of the time, which would eliminate most of any looseness or mild bump stop deterioration.


Norm

 

[pass1over]

bump stops have been trimmed down to compensate for lowering, car is definitely not riding on the bump stops at all. I've verified with car on lift, supported under axle. Plenty of travel room between axle and bump stop while normal travel.

I can load everything back in the trunk and see where it sits, but it only pushed the rear down by about 3/8".

I did hit a very rough spot at the wrong angle (and way too fast), and heard the left bump stop contact frame, because I hit it so harshly/fast. I really doubt it was riding on the bump stops while loaded, but I can check it out.

 

[Unexplodedcow]

both of em, lol

actually, it was 3 - 50# bags of corn and 3 golf cart batteries that are about 60lbs each. Other 3 were on my front passenger floorboard.

You're a brave man to marry golf cart batteries and bags of corn.

 

[Unexplodedcow]

I finally had some help and was able to crawl under the car and determine the source of the clunks.

At this point, none of the bolts were loose - hooray, I solved that issue. Thread locker plus jam nuts....that is unlikely to come loose.

The real source of the clunks was obvious once I got the car jiggling enough, as it was visible, granted it was 1-2mm, but still just barely visible when watching. It turned out the delrin liners in the roto-joints had worn/cold-flowed, and was tight when reassembling, but would work itself into a specific position that it previously worn into.

There was black galling, it's possibly some delrin that was burnt and transferred to the UCA roto-ball. Also, of note, that one collapsed in a bit, and the whole upper bracket did, too, by about 1/8" so it's not even usable with the stock or any other UCA.

I bought a replacement J&M UCA/LCA setup. Unfortunately, they sent me two driver-side LCAs, so that needs to be fixed, but the UCA works, came with stepped anti-clunk washers to use with the stock UCA bracket, which I still have. The lowers are some older used arms, but it *should* work. I can confirm that the larger Prothane bushing sleeves fits and holds up extremely well with high clamping force, and the weld washers I soldered in have no moved, no cracking of solder, either. Still wish I had a welder, but perhaps in the future. It's working as it should, so no complaints.

I hope this puts things to rest, but can say that 1500ish miles on the roto-joints caused some extreme wear, despite multiple lubings and ensuring they were snug. The balls were not only moving in the liners, but the liners were also moving in the control arm bores. I never would've seen it without having help to wiggle the car back and forth with the parking brake on.

I've had much, much better longevity out of urethane bushings or even spherical bearings. Don't know why the Delrin wore so poorly but I now know. My paperweight collection grows. At least that $800 DSS piece has friends.

 

[GriffX]

Did you get some unusual wear or NVH problems with the LCAs? I have the J&M Extreme LCAs and they improved the drivability a lot. But, I think I have some new NVH issues related to. Got lots of high frequency vibration in the whole chassis, can see it in the rearview mirror.
Thanks!

 

[pass1over]

those look like solid bushings on the J&M extreme's. If so, you will definitely have some more NVH than the stock squishy rubber ones.

 

[GriffX]

those look like solid bushings on the J&M extreme's. If so, you will definitely have some more NVH than the stock squishy rubber ones.

Of cause, but its acceptable. When I installed them I had bad vibration, over torqued the front bolts (reused) a bit and it stopped. After 10kmi it started again but only at high speed (85 mph). The bolts did not came lose, so I'm looking for the cause and no idea.

 

[Unexplodedcow]

The J&M Extremes use a polyurethane bushing on the ball, which should hold up better. I had their polyball versions a while back and put a lot of miles on them - they worked fine, too, so I suspect their extreme joints will do nicely. Urethane is at least less likely to cold flow or wear in place than delrin.

The bolts can be reused as they are not at the yield point. What may have happened is you had either a sleeve collapse, or the sleeve slightly extruded through the large chassis bolt hole, which is what happened with me. The only workaround I found was to get some Prothane bushings for the stock arms, and they come with the proper width sleeve that's roughly double wall thickness compared to anything else, very close to OE. I then bored out bushings in, say, the UMI arms, to fit the sleeves, and that worked.

For my car, the inner chassis holes were damaged. I reamed them out to fit stepped weld washers, which I then soldered in (no welder available), and switched out to 9/16 18 thread hardware using Humvee lug nuts with orange loctite and grade 8 jam nuts behind that, and torquing on the heavy side of OE (yield torque would be around 170 for the bolt). I have not had this back off or even remotely loosen, and the sleeves will not collapse. I wish all aftermarket brands used a large inner sleeve - it would likely solve a lot of problems.

 

[Unexplodedcow]

Update:

It's been a month - the car is clunk free. Not being able to re-use the UMI body bracket due to collapse kind of sucked, but the stock one works just fine, even with the spherical bearing in the diff and J&M extreme joint UCA.

As "luck" would have it, I received two driver-side LCAs, so back those go. Using some old J&Ms I had sitting around, with the modified front bushings.

For what it's worth, the Prothane crush sleeves, combined with 9/16-18 bolts, soldered-in step washers, and using the orange loctite + extra jam nut worked out extremely well. There have been zero issues whatsoever, and I have not been kind over bumps, or whenever I want to play.

The panhard bar is also a UMI roto-joint. Replacement is planned, though the bar itself was taken apart, and shows no damage to either the ball or the liner. No collapse, either, but given the wear on the other arms, I'm dubious.

Either way, when in doubt, it might just be the bushing inside the arm causing the clunk.

 

[Nick Thompson]

I wanted to resurrect this if I may. I am chasing down a clunk, but mine is literally only when backing out of the driveway (and it's like how is this possible, the car isn't even moving). I have not driven my car much bc of it, and have had the parts installed for quite some time (but no more than 500mi). Hard launches, no issues. NVH sucks in 6th at 75mph, but that's what radios are for.

I have the UMI relocation brackets, UMI poly/Roto LCA's, Steeda Adjustable P/h Bar (race, so it too has rod ends/heim joints), Steeda P/h bar support, UMI Upper CA, Stock Bushing in the Diff, koni sa's, Steeda rear adjustable sway bar and Steeda Springs (race) with the GT500 bump stops.

@Unexplodedcow: Do you have any pics of what a collapsed roto-joint looked like off your car? I put all of my hardware at 130 ft/lb bc doing the UMI spec had me convinced the rear end was going to fall out of the car it clunked so bad. I am fearing I might have this issue but was curious if it's obvious by looking at it, or do you need a "before" and "After" source to tell the difference.

 

[Flusher]

I put all of my hardware at 130 ft/lb bc doing the UMI spec had me convinced the rear end was going to fall out of the car it clunked so bad.

Is there a substantial difference between outside diameter of your hardware and the inside diameter of your roto-joints?

If I'm understanding correctly, over-torquing the fasteners made the "clunk" less severe. That leads me to believe that there is a mismatch in fitment between the joints and fasteners and that the additional clamping force, of the fasteners, is producing less movement of the because of increased friction between the joint and the bracket.

We run larger than stock fasteners and ream the holes to the nominal size of the bolt. That way, there is only a few thousandths of an inch of clearance total, per joint.

 

[Nick Thompson]

I'll put the car in the air tomorrow and check, I honestly can't remember.
I'm running whatever hardware UMI supplied me with through the roto-joint at their relocation bracket. Their instructions advised to use the OEM hardware (through a sleeve) at the upper part of the relocation bracket (where the stock LCAs would attach) and also where the poly end of the LCA bolts to the body. Based on this thread, it sounds like that could also be an issue and I've noted the fixes some of the others have posted.

 

[Flusher]

A lot of companies will use tubing, which doesn't fit the bolts really nice. The company, that I work for, race preps side-by-sides. For the suspension bushings we make, we bore solid round bar to the correct size. In some cases, we oversize the fasteners for better fitment (and strength).

I haven't pulled my rear suspension apart yet, but I have done many muscle cars. The OE rubber suspension bushings are serrated to bite into the brackets when the fasteners are torqued. The inner "tube" in the OE rubber bushings is a rolled piece of sheet metal, not a tube and definitely not precise.

Just a thought.

 

[pass1over]

I have replaced most of the rear suspension hardware with properly sized hardware. Flusher is correct, a lot of the stock hardware is/was VERY sloppy in the bushing holes. At the time, I worked for Fastenal, so it was super easy for me to find hardware that fit better.

I found a lot of it switched to the similar sized fractional bolts and they fit much better, but it didn't solve the rattling/clunking problem over small bumps in my case.

I'm almost positive, the reason it clunks now is your aftermarket LCAs. They all seem to have a slightly shorter than stock inner steel bushing. I measured the length of it on my Steeda billet LCAs and my stock LCAs that are still on my shelf, and it was a few mm shorter. You can't get a good clamping force with it being too short, so it rattles/clunks. The same could be happening on the UCA, but I haven't investigated it yet.

 

[Unexplodedcow]

]

I wanted to resurrect this if I may. I am chasing down a clunk, but mine is literally only when backing out of the driveway (and it's like how is this possible, the car isn't even moving). I have not driven my car much bc of it, and have had the parts installed for quite some time (but no more than 500mi). Hard launches, no issues. NVH sucks in 6th at 75mph, but that's what radios are for.

I have the UMI relocation brackets, UMI poly/Roto LCA's, Steeda Adjustable P/h Bar (race, so it too has rod ends/heim joints), Steeda P/h bar support, UMI Upper CA, Stock Bushing in the Diff, koni sa's, Steeda rear adjustable sway bar and Steeda Springs (race) with the GT500 bump stops.

@Unexplodedcow: Do you have any pics of what a collapsed roto-joint looked like off your car? I put all of my hardware at 130 ft/lb bc doing the UMI spec had me convinced the rear end was going to fall out of the car it clunked so bad. I am fearing I might have this issue but was curious if it's obvious by looking at it, or do you need a "before" and "After" source to tell the difference.

It sounds like you have a similar setup as my car, so I can hazard a few guesses. Oh yeah, I also had to replace the roto-joint on the pandhard bar, as it was causing side-to-side clunks. It was also the Delrin liner that had cold-flowed and stuck, causing binding and wear, which lead to slop. I replaced just the end with a regular UMI urethane bushing, and it's doing fine; no clunks or issues.

The LCA roto-joints absolutely will start collapsing with anything beyond ~90 lbs. of torque. Their torque spec is necessary to prevent that collapse. I've included some photos to show how things went on my end.

This is one LCA crush sleeve. Stainless, but slightly corroded. Notice how the stains don't show much movement? That's because the crush sleeve was spinning, not the bushing. This was due to too low of torque, and happened despite tons of grease.

Here the small amount of extrusion damage is visible. The torque box on the car was worse, as the sheet metal had basically collapsed through, so I had to install the stepped weld washers to reinforce (they're still working great).

My solution: I bought a Prothane rear LCA bushing kit for the OE arm, and it came with appropriate crush sleeves. Frankly, they are the *only* ones doing it right on the crush sleeve wall thickness. I bored out the UMI bushing to the 1" needed for the OD of the Prothane sleeve, and put it back together. It's removed in this picture as I did the same mod to the J&M arms I put back on the car. Every arm maker uses the smaller crush sleeve, and I was not having the same problem again. A thick-walled crush sleeve is necessary, IMO.

The first failed roto-joint. Notice how the spaces between the ball and ends are bulged outward. This is due to OEM torque values being applied in the MM relocation brackets. They collapsed forward, as there was some angling and imprecise fitment.

The 2nd LCA roto joint - Note the galling and blackened appearance. This is not grease. I tried the supplied grease, marine grease, and went to SuperLube PTFE-based grease (same stuff as used by Prothane and Energy Suspension). The collapse isn't as apparent, but I still had the clunk.

Here is the UCA roto-joint. Note the extreme galling. What I can say is that UMI made their M14 bolt hole precisely, and the OE bolt fits perfectly without any jiggling. The same can't be said for the center of the roto-joint, as it easily takes 9/16 hardware (slightly larger). It, too, slightly collapsed, and while it's not really visible, it was bad enough that it *also* collapsed the 1/4" thick steel mounting bracket I also bought. Spoiler: I can't use it and it's trash due to being bent, and I do not trust bending it outward - not in that application.

I went back to the stock UCA mount bracket, and used stepped washers to properly fit a stock M14 bolt, with a new J&M "extreme" style UCA. I torqued to OE specs (per their instructions), and have seen zero issues from it.


Here is the real culprit and cause of the roto-joint clunks (aside from the torque values and collapse problem): the liner material. UMI uses Delrin (POM/Acetal if you prefer). Nothing wrong with that. It's a solid material that machines and wears well. Technically, poly is more durable in a cold-flow and shock load situation from what I've read (haven't tested it). J&M uses poly liners for their polyball as well as extreme joint arms. I've driven the car more in the past year than I have in the past 5, and the J&Ms have already outlasted the UMI arms.

What can be seen in the above picture is how the delrin has been worn in by the threading inside the arm. This is a big problem, and means the delrin is cold-flowing under pressure, and explains the galling. Not great.
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After a year of pondering, driving the car, and inspecting it repeatedly, plus tearing the thing apart probably 30 times the past few years (especially last summer, where it spent the time with its butt in the air, and the rear axle out), I have some ideas on the causes.

1. Insufficient torque. Bolts themselves aren't strong in a sheer load compared to a clamping load. The idea is that enough compression/friction is created by the bolt to overcome sloppy tolerances, and still allow proper pivoting. If that torque load fails, however, you get a badly sloppy joint.

Loss of torque can happen from bolt stretch, or material compression/extrusion through whatever is being clamped. This happened on the crush sleeves, and fixing it is a relatively simple task.

2. Roto joint balls are thin-walled between the ball and flange "ears" on either end, and are prone to collapsing with an uneven load applied. This is a material or design issue. I had a friend who was going to make me some new roto balls, but instead of the stepped "ear" design, it was going to taper down to the stock thickness at the ball, allowing for a much stronger ball (and limiting some of the movement, which is more than enough anyway). He was going to make it out of IHCP (meant for hydraulic pistons) and we were discussing how much to harden it for auto use (specifically with the shock loads on the suspension).

3. Use a different joint liner material, urethane, or something that's less prone to cold-flowing. Kind of a tall order, especially where grit and dirt are concerned. Spherical bearings aren't exactly known for lasting a long time on the highway, but if they're maintained, it's good. Speaking of, so far, so great on the Steeda diff. spherical bearing.
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If you torqued to OE - you'll need to replace the Roto-joints themselves, and get a rebuild kit from UMI. Just the LCAs will probably cost $50 to your door. However, you may also need front bushings/crush sleeves if you torqued to OE and it's started extruding through the chassis. Give it a really good look, measure the hole diameters, and look at the ends of the crush sleeve.

Either way, I highly suggest doing the Prothane mod I did. As for boring out the bushing, I used a drill and went slow, to avoid sticking and tearing. It turned out reasonably smooth-bored inside, but with enough surface area to allow grease holding. Again, hasn't given me a problem in a year. I would say to do this with any aftermarket arm design that uses the small crush sleeve.

As for the roto-joint end - well, unless you have custom bits made, that is (IMO) kind of a lost cause, and I would suggest getting new arms from another maker (Steeda, BMR, J&M, OE, or a Prothane OE-style rebuild kit). I'm not a fan of poly at both ends, and found the J&M polyball to be a decent "in between". Again, needs that front bushing made larger, but the rears work fine, and don't collapse (carbon steel vs. stainless compared to the UMI).

I know - this is a very long response. Hopefully it gives you some ideas on how to stop the clunks.