S197 rear LCA Torque Box bolt hole ovaled

[lsxjunkie]

2014 Mustang GT, 86,000 miles.

About a year ago I started to feel the rear of the car steer under braking. I swapped out my rear LCAs for J&M tubular LCAs with the rotoball rubber/poly bushings.

When I went to remove the OEM LCAs driver's side body end bushing crush tube was seized to the lca bolt. I ended up destroying the bushing before limping the car to a dealership to have the old bolt cut out. I fear they may have damaged the torque box then, but I didn't have any trouble all year with the J&M LCAs, so i put it out of my mind.

This past Friday i start getting a good clunk under hard braking and in reverse from the same torque box, along with the same rear steer sensation. I get the car on a lift today and it turns out the inner bolt hole has ovaled and the bolt is moving around under power and braking.





The shop said I can weld in a plate and drill a new hole. I have concerns about proper alignment if I do this.

I see that Lakewood Engineering sells a torque box brace which you weld in and bolt through. Is this a viable alternative or would they not be strong enough to bear the longitudinal loads?





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[blacksheep-1]

IMO you are on the right track with the brace, I've had similar issues with fox bodies over the years and this is a great way to fix it. If you are concerned about the alignment run a "sacrificial" bolt/ tube end in place, do the welding and then remove it. As for strength, you've essentially doubled the thickness of the material so it should be fine. The only long term effect that comes to mind may be corrosion between the metal panels after welding, you can get around this by using weld-through primer, then painting over it.

 

[lsxjunkie]

IMO you are on the right track with the brace, I've had similar issues with fox bodies over the years and this is a great way to fix it. If you are concerned about the alignment run a "sacrificial" bolt/ tube end in place, do the welding and then remove it. As for strength, you've essentially doubled the thickness of the material so it should be fine. The only long term effect that comes to mind may be corrosion between the metal panels after welding, you can get around this by using weld-through primer, then painting over it.

Thanks for the quick reply. I was thinking the same. My only concern is that the brace was meant to work in conjunction with the torque box. On the side that is ovaled, the brace will end up bearing almost the entire load. I don't want to end up with a brace that is ovaled or torn as well.

Although, from the looks of it, the brace appears to be thicker that the torque box itself. Is it likely to be stronger and I'm just overthinking it?

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[blacksheep-1]

You could weld the hole shut and using the brace, mark and redrill it, if you have access to it.

 

[Grant 302]

I like Rob's suggestion, but if the outer hole is still good/round, I don't think you should have much of a problem re-drilling the inside one.

Good luck with the repairs.

 

[lsxjunkie]

Thanks again folks. Ordering now.

 

[Fabman]

I would just weld a washer over the hole and be done with it.

 

[302 Hi Pro]

I suspect a loose bolt/nut caused the issue, this is why I use blue threadlocker on all my suspension fasteners.

You could also weld the torque arm brace to each torque box. If you do weld, take BlackSheep-1’s advice and use the special Welding Primer on all exposed metal before you weld.

Good luck with this repair & let us know what you decide to do.

 

[Norm Peterson]

I suspect a loose bolt/nut caused the issue

Not "loose" as measured by fastener installation torque used, but I'm pretty sure it's a related reason.

I'll bet a virtual $20 that the poly bushings are longer than the inner sleeves that run through them. When this condition exists, some (maybe a lot) of your installation torque is wasted in trying to compress the polyurethane. That means that the clamp load through the actual joint (bracket side / inner sleeve / other bracket side) is not as high as it is supposed to be and is far more likely to slip under acceleration or braking loads.

Keep in mind that the poly bushing wants to remain fixed on its outside diameter to the LCA, and that under vertical suspension movement the bushing will be rotating relative to the chassis bracket sides. This makes sliding over however much bolt hole clearance even easier, and when it bottoms out on the edge of the hole that's your 'clunk'.

Shave the poly down until it is just a little shorter than the inner sleeve (a hundredth or two should suffice). Better still, shave the flat faces into very flat cones, which will allow a little rotational compliance where there was zero before - even a 3-link with longitudinally-oriented LCAs benefits a little in terms of "roll bind". Since it's almost invisible once installed on the car even a bench grinder can be used to grind away this "unwanted" material. Long-term bushing material durability *might* take a small hit, but bushings in general (and aftermarket bushings in particular) should be considered wear items anyway.


On edit, if the hole hasn't gotten too big or too far oval, you may not need to do anything to the bracket. Once you're not compressing the poly, all you need is enough bracket metal to support the inner sleeve in 'bearing'. But I have a solution if the hole has gotten too big.


Norm

 

[racer47]

If you are still deciding, here is the steeda torque box brace for $200

http://www.s197forum.com/threads/steeda-mustang-frame-rail-torque-box-brace-555-5551-05-14.133834/

 

[Norm Peterson]

If you are still deciding, here is the steeda torque box brace for $200

http://www.s197forum.com/threads/steeda-mustang-frame-rail-torque-box-brace-555-5551-05-14.133834/

If it fits outside the OE chassis-side bracket, the matters of clamp load and support for the inner sleeve at the still-ovaled bracket hole are not resolved. This piece probably has merit, but not as a repair for this kind of wear/damage.


Norm

 

[lsxjunkie]

Not "loose" as measured by fastener installation torque used, but I'm pretty sure it's a related reason.

I'll bet a virtual $20 that the poly bushings are longer than the inner sleeves that run through them. When this condition exists, some (maybe a lot) of your installation torque is wasted in trying to compress the polyurethane. That means that the clamp load through the actual joint (bracket side / inner sleeve / other bracket side) is not as high as it is supposed to be and is far more likely to slip under acceleration or braking loads.

Keep in mind that the poly bushing wants to remain fixed on its outside diameter to the LCA, and that under vertical suspension movement the bushing will be rotating relative to the chassis bracket sides. This makes sliding over however much bolt hole clearance even easier, and when it bottoms out on the edge of the hole that's your 'clunk'.

Shave the poly down until it is just a little shorter than the inner sleeve (a hundredth or two should suffice). Better still, shave the flat faces into very flat cones, which will allow a little rotational compliance where there was zero before - even a 3-link with longitudinally-oriented LCAs benefits a little in terms of "roll bind". Since it's almost invisible once installed on the car even a bench grinder can be used to grind away this "unwanted" material. Long-term bushing material durability *might* take a small hit, but bushings in general (and aftermarket bushings in particular) should be considered wear items anyway.


On edit, if the hole hasn't gotten too big or too far oval, you may not need to do anything to the bracket. Once you're not compressing the poly, all you need is enough bracket metal to support the inner sleeve in 'bearing'. But I have a solution if the hole has gotten too big.


Norm

Someone owes you a virtual 20 dollars. The J&M bushings are wider than the crush tube by a few mm. I believe they're designed that way so the bushing and crush tube rotates with the arm instead of being fixed to the body like the factory LCAs. I was blinded by the fancy rotoball axle side bushing that I never considered that having the bushing wider than the crush tube could be an issue.

I should have gone with the whiteline LCAs. The crush tube on those is wider than the bushing and does not move with the arm. There is a ptfe liner between the crush tube and the bushing that allows articulation.

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[Norm Peterson]

Someone owes you a virtual 20 dollars. The J&M bushings are wider than the crush tube by a few mm. I believe they're designed that way so the bushing and crush tube rotates with the arm instead of being fixed to the body like the factory LCAs.

You may be right, in which case the people designing this sort of connection simply do not understand that the kind of joint that has to permit rotation is not supposed to rotate about the bolt or load it in shear. Even though that's the way it probably looks to somebody who isn't sufficiently engineering-oriented to recognize that clamp load and friction are also involved (and that the friction effect works best at zero movement of the sleeve).

It's not just J&M, either (first time I saw this design was with some poly LCA bushings I bought way back in 1988 for a 1979 Chevy Malibu, and I knew it wasn't the right approach as soon as I took them out of the box). So maybe most of the blame belongs with the first entity that came out with poly bushings and only a little with the rest who simply copied the first guy's design. After all, it is the simplest/cheapest design . . .

Norm

 

[lsxjunkie]

You may be right, in which case the people designing this sort of connection simply do not understand that the joint is not supposed to depend on the bolt being loaded in shear. Even though that's the way it probably looks to somebody who isn't sufficiently engineering-oriented to recognize that clamp load and friction are also involved (and that the friction effect works best at zero movement of the sleeve).

It's not just J&M, either (first time I saw this design was with some poly LCA bushings I bought way back in 1988 for a 1979 Chevy Malibu, and I knew it wasn't the right approach as soon as I took them out of the box). So maybe most of the blame belongs with the first entity that came out with poly bushings and only a little with the rest who simply copied the first guy's design. After all, it is the simplest/cheapest design . . .

Norm

Do you have a suggestion for a properly designed LCA for a 20k mile a year daily driver. NVH and longevity are my goals, but I am also not a fan of the oem lcas. No drag racing, lots of twisty roads. I'm at 87k miles now and I'd like to go another 87k at least.

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[Norm Peterson]

My opinion - the best overall choice for an S197 uses a spherical joint at one end - preferably not a rod end/Heim joint - and either a lightly modified poly or 3-piece poly bushing "sandwich" in the other end. I'm personally running a set of Johnny-Jointed Currie Currectrac (sp?) LCAs in my '08, and have for a little over 5 years at this point. They're still quiet/don't transmit enough road or differential gear noise to hear over the stock exhaust. A couple times a year I shoot some lube into each end and call it done. The car sees year-round street driving and track driving whether the day is clear or rainy. It'd be on the track tomorrow except that the event got canceled #BecauseSnow.

Yes, I did do the bushing length/flat cone mod to the poly. What I don't know is whether the Curries are still available. UMI or Spohn may have something similar, though.


Norm

 

[Grant 302]

You may be right, in which case the people designing this sort of connection simply do not understand that the kind of joint that has to permit rotation is not supposed to rotate about the bolt or load it in shear. Even though that's the way it probably looks to somebody who isn't sufficiently engineering-oriented to recognize that clamp load and friction are also involved (and that the friction effect works best at zero movement of the sleeve).

It's not just J&M, either (first time I saw this design was with some poly LCA bushings I bought way back in 1988 for a 1979 Chevy Malibu, and I knew it wasn't the right approach as soon as I took them out of the box). So maybe most of the blame belongs with the first entity that came out with poly bushings and only a little with the rest who simply copied the first guy's design. After all, it is the simplest/cheapest design . . .

Norm

Hear, hear! I've been a long time opponent of poly bushings in the trailing arms. SN95 'quadra-bind' was my first concern with them.

Ditto for the 3 link/panhard S197. I wouldn't put poly in any of it except for the panhard, which shouldn't need to twist much. I remember getting a fair amount of push-back on the subject, until poly failure in the upper and lower became more common. I used to think the poly-balls should be okay, but it seems they might have designed them with too much pre-load on the bushings. I'd only use heim joints (edit: or del-sphere) or rubber bushings in any of the trailing arms.

 

[lsxjunkie]

Daily driver indeed. My commute home tonight was 45 minutes of this.

 

[lsxjunkie]

I got an appointment to weld in those braces, but I'm going to replace the LCAs too.



Thoughts on these Whitelines? They say the bushings are synthetic elastomer...isn't that just a fancy name for polyurethane? The crush tubes are designed to be fixed to the torque box; the bushings rotate around them with the PTFE liner.

https://www.americanmuscle.com/whiteline-fixed-rear-lca-0514.html

It's a toss up between these or just going back to OEM at this point. They're the same price.

 

[Grant 302]

Those should be better than the previous style of Whiteline arms (with the big yellow bushings). A lot of LCAs now seem to have been redesigned more like the Eibach ones...hrm.

 

[Norm Peterson]

Thoughts on these Whitelines? They say the bushings are synthetic elastomer...isn't that just a fancy name for polyurethane? The crush tubes are designed to be fixed to the torque box; the bushings rotate around them with the PTFE liner.

https://www.americanmuscle.com/whiteline-fixed-rear-lca-0514.html

If you look at the close-up of one end, you'll see that the bushing is contoured such that there is a little flexibility in the twist-direction of the LCA itself and little or maybe no bushing material as long as the sleeve. The intent is to add some flexibility in at least one direction without compromising stiffness in the direction(s) that you want relatively high stiffness.



While I don't know anything about WL's material itself, it is an example of voided-bushing technology (normally an OE-level tactic). Just at the aftermarket level rather than OE, which if you look at the OE Ford LCAs you'll see something similar at work. Ford and Whiteline probably feel that some additional compliance needed to be designed into the bushing shape because neither of them are using any spherical at all.

Incidentally, these inner sleeves really aren't 'crush sleeves' in the same sense as crush sleeves used for pinion preload in a differential. I'd defy anybody on the planet to actually manage to crush or collapse an aftermarket control arm bushing's inner sleeve. In OE versions, there typically are little 'nubs' that actually get forced into the bracket sides creating little dimples there.


Norm