[Two_70_Converts]

Originally Posted by Half-Inch Stud

Fender Paint all good?
Rim good?

Yep, no other damage luckily.

[phil400]

Atleast no one was hurt and no damage, pretty lucky.

[squidtone]

Glad everyone is okay and the damage is repairable.
This same failure happened to my 67 GTO to the previous owner. The underside of the front frame crossmember had gouges, the core support and fenderwell had some mangled sheetmetal from the "loose wheel". Messy failure.When I restored the car I noticed one lower arm had the classic junkyard yellow marker writing so it was a used replacement. I try to keep an eye on those arms once in a while.

[Drag Star Le Mans]

Damn good thing he was driving at slow speeds, that would have been bad otherwise. Never seen a failure like that! Time for some inspecting seeing how I have an 1 1/4 swap bar on front and have pounded my car pretty hard.

[dataway]

Imagine if it happened while hard on the brakes at 60 mph.

Yep, glad no one was hurt and no major damage.

[242177P]

This, and the earlier one, have something in common... Loose endlinks.
Poly is tough, and if you let it have a running start, it will pound the hell
out of anything in it's path. And check out what the bolt did to the arm.

[geeteeohguy]

Originally Posted by 242177P

This, and the earlier one, have something in common... Loose endlinks.
Poly is tough, and if you let it have a running start, it will pound the hell
out of anything in it's path. And check out what the bolt did to the arm.

X2. The ONLY time I have seen A arm failure on A body GM cars over the past several decades is when the stock rubber bushings were replaced with poly bushings. No thank you.

[bigkel]

I have seen that on a Cadillac . wide radial tires put more load on that area than it was designed to handle .

[Scarebird]

End links did not cause this. Most likely a nick or gouge on the lower edge of the A-arm. Bottom edge of the arm between spring pocket and ball joint is of course under tension.

[Shiny]

Originally Posted by Scarebird

End links did not cause this. Most likely a nick or gouge on the lower edge of the A-arm. Bottom edge of the arm between spring pocket and ball joint is of course under tension.

I also don't see how a stiffer bushing or loose links could affect loads at the location of the failures. Seeing two broken in the same location is unexpected though. Wonder why they both broke there? The design must have highest stress at that point or there is a forming defect. I think the near-identical location of fail shown in both images is not a coincidence.

Neither photo shows much bending around the fracture. This is also surprising to me. I would expect the break to start along the bottom edge as you say, propagate up, then have the whole arm bend up. I wonder if these arms were made of something stronger than low-carbon steel?

[U47]

Originally Posted by Two_70_Converts

My son decided to get his Mom out of the house for a "fun" short drive. It didn't end well. Tire was sliced open, tie rod bent, shock blew out and of course the obvious. Luckily one of the rare times he wasn't going fast and on a back road. Never had one break at the ball joint before.

I have 69 H-O LeMans that I bought new. When it was about 2 months old I went to the local McDonalds, while standing in line to order food a big bang went off, I turned around to see what could make such a loud noise. It was my car and the rt. ft. was on the ground the rt. ft. upper "A" arm was broken in half and just about the same distance as your car from the ball joint. The car had less than 2K on the ODO. Under warranty the car was towed to the dealership. My buddy worked there ( he's the one who did the PDI on it ) and he told me that this kind of thing had happened before.

[autobahn]

when first formed there are some ripples in the metal, if these ripples are smooth at the edge , but if there are rough or a jagged edge that is a possible point of fracture my bet is with this situation

[Tempest]

if the end links caused this then the crack would have gone to the end link hole.

I agree with Scarebird, don't blame the poly bushings.


I would think that this has been cracked for a while, and slowly increased in size until it finally broke all the way off.