Strut Rod Bushing Failure - Causes?

[73_Cuda_4_Me]

 

Rebuilt front suspension on the 73 this spring after frame rail repair on driver's side. New LCA bushings, sway bar end links/bushings, and strut rod bushings. All Moog bushings.

Been a great summer and fall for cruising, and we took about 200 mile trip yesterday. When I was out in driveway this morning, found part of the passenger side front strut rod bushing laying there. the front bushing has a little collar that sits inside K'member, with concave washer holding in place. Nut was tight, pin in place, and center steel sleeve still in both portions of bushing centers. The collar had blown apart and the bushing split, and somehow popped out just outside the garage door.

Anyone had this happen to them lately? The car is used strictly for cruizin with better half, no constant lead-footing, just the occasional tromp now and then during acceleration...

It's only got 1800 miles on the bushings... everything was torqued, driven for a week, re-torqued, then pinned. Car is sitting normal height with original TB's. Driver's side bushings are perfect as I would expect with mileage on them. No sign of problems with k-frame hole that bushing sits into, and only thing seen is when jacked up with LCA full down, strut is at pretty good angle up going forward  toward bottom of radiator...

Any ideas on what would cause a failure like this? I haven't even had it jacked up all summer.. it's just driven so smooth since frame rail and LCA bushing change that I haven't had to do any work on it! (And that is somewhat depressing for a true car nut!)

[GY3R/T]

Maybe just a bad bushing. IMO, Moog quality isn't what it used to be. If you have thoroughly checked LCA and pin bushings in K-member and K-member reciever hole (welds), then i would simply install new bushing/bushings and keep an eye on it. BTW. Which way did you install concave washer ?

[73_Cuda_4_Me]

New moog bushings will be at the auto shop in the morning, and the cup of the washer was toward bushing, so it was just compressing bushing out the sides when torqued...

Like this...

  {0|0}  Cup washer, bushing, k-member, bushing, cup

[1 Wild R/T]

MOOG K7026 should have the washers installed  like this....      -)I(-

[73_Cuda_4_Me]

Understood, 1 Wild... these are the K7016A bushings... they are the 'standard' design...

I had read about the differing installation for the Belleville washers depending on type of bushing in various threads here and other mopar sites. I made sure that they were put on according to the way the old ones came off and the type that I put on last spring.

[purple1]

I can't tell you what the cause is. I have no idea. But I had the same thing happen with PST polygrahpite strut bushings. One just split and fell off at the gas station one day. I tried to get them to honor the lifetime warranty and being 10 years old they refused without a receipt. I ask them who keeps a receipt that long. They said the records didn't go back that far. 
The car only had a few thousand miles on it since replacing the bushings. I just picked up some new polyurethane bushing and moved on.

[Brads70]

Maybe over tightening or over compressing poly causes them to split? Wired that that also happened to the moog rubber ones though. No idea why that happened? 

[Chryco Psycho]

The parts may have sat on a shelf for years before they were installed too

[1 Wild R/T]

FWIW I always use the K7026 bushings, I consider the accurate positioning of the strut rod to important to trust it to the cheaper bushings, as far as using polyurethane there?  Well a couple issues with that.. Most are thicker than the OE bushing when compressed since the poly doesn't compress much, that means the lower control arm is being pushed further rearward which reduces caster, you know all that caster we work to add?.... Second because Poly doesn't compress much if at all it also doesn't allow the strut rod to move freely... But the strut rod has to move when the suspension moves.... So something has to flex.... 

I've never seen a Mopar do this but they have thicker strut rods than Fords... The fact it's happened to a lot of Mustangs gives an indication of the force applied to the strut rods when you use poly..

[73_Cuda_4_Me]

Thanks for this, all... The reason I went with standard design was to keep away from the poly in this area...

The poly rear spring bushings and shackle bushings seem okay for use by a lot of people, but I think it's the orientation that makes them acceptable for those (load force perpendicular to bushing, so firmness helps suspension be more solid, and yet there is lots of give to the springs and shackles to minimize poly bushing's harshness).

In the strut bars, it's a push/pull parallel to bushings, and there would be no give for that, or in compression of mounting. That would impact caster as 1 Wild states.

As far as being too tight as a cause, the steel spacer sleeve prevents that... the washers on either side of bushings stop solid against the sleeve ends.. I get just a little bulge on each bushing when it's torqued.

I made sure to put silicone grease (doesnt' react with rubber) on the bushings, and jacked LCA up so strut was level when installing the fronts. Made sure the collar of fronts meshed completely with the counterbore of the rears. We'll see how long these last...

Just that the whole thing would have gone unnoticed if it hadn't fallen off in the driveway... not sure how big of safety issue that would be on the open road in a panic stop situation??

[1 Wild R/T]

You would notice it pretty quick between the brake pull & the clunking....

[73_Cuda_4_Me]

I figured that a clunk would be an indicator, but pulling during braking makes sense, and will keep that in mind as well... I'll also inspect every time it is up in the air, too... just to be sure...

Thanks for the input, everyone!

Time for some more color tour of West Michigan!

[1 Wild R/T]

The strut rod transfers brake force to the K so typically the front side of the bushing takes the most abuse...  If it fails the caster moves all over the place.... So the car can dart right or left when you hit the brakes.... 

[73_Cuda_4_Me]

Thanks 1 Wild R/T...! Your knowledge sharing with all the rest of us is greatly appreciated!

[jordan]

Same thing happened to me within the first 1000 miles after getting my car together.  I do drive more aggressive, but assumed the bushing would last more than a little while.  I made sure it won't happen again, and bought Hotchkis strut rods with a heim joint and no bushing to fail.  The car does not have any clunks and the steering and braking are very precise. 

    When my old bushing failed, I was at an autocross track for the first time.  When braking hard, the car would lock the opposite tire and pull toward the broken bushing side. No clunk sound.