Broken Bolt FYI

[scootter]

Just an FYI for something to check.

The other day my wife said the car was making a clunking noise by the rear end ( she has to tell me the noise's the car makes since I can't hear sh?t). Had the car up on stands since I was changing the oil and knew to check the bracket on the rear end since the bottom two bolts came loose before. All was good so figured she was hearing something else. Went to go get gas the night before our road trip when she told me again ( thank god she went). So I took at my ear plugs and could hear it. Put he car up on the stands again and was a bit confused when I looked up on top of where the rear third member bracket hooks to the frame. The top bolt was sticking out about an inch. No problem. Pound it back in and put a nut on it. NOT! The end of the bolt was sheared off. Mind you, this is a M12 8.8 5" long bolt. Try to find that late on a Thursday night, let alone early Friday. The third supply house had a 4 1/2" long one that barley got me by to do the trip. I did order a new one with a longer shoulder from Mc Master Carr that is 5" and will have no thread in the bushing or bracket to hopefully cure the problem.

The car has 34k miles with a lot of spirited driving. So remember to check those bolts. I hate to think what could/would have happened if it came all the way!!!

Scott

[Randy Rosenberg]

I'm glad you found it, before it finding you...

[CWizard]

Pardon my ignorance, but could you please tell me more about where the "rear third member bracket hooks to the frame" is located, and what is a "rear third member"?
Many thanks!

[Got the Bug]

Originally Posted by CWizard

Pardon my ignorance, but could you please tell me more about where the "rear third member bracket hooks to the frame" is located, and what is a "rear third member"?
Many thanks!

Scott,

Maybe you can post a couple of pics to show what's going on.

Thanks.

[scootter]

Shows how well I check my writing.

It is the bracket that holds the back of the differential to the frame. It is bolted to the back with two bolts then goes up on top of the frame. I have a temporary bolt in there now and hopefully changing it tomorrow. I will take some pics of the bracket. The one that was in there didn't have a long enough shoulder to go all the way through the bracket. It snapped right at the end of the threads. The new bolt has a longer shoulder to go all the way through then i can put a washer and a distorted thread lock nut on it.

Doug, do you need any other pics while I have the car up in the air?

Scott

[Got the Bug]

Originally Posted by scootter

Shows how well I check my writing.

Doug, do you need any other pics while I have the car up in the air?

Scott

How about the whole underside of the car. You know, like the under-carriage cam that they have at Barrett-Jackson.

[Silverback51]

This is the bracket he is referring to if I understand him correctly.

By his discreption, the bolt that broke is the one that went through the rubber isolater bushing.

Generally it's a bad engineering design that puts the threads of a bolt in shear. Seems this is one of the issues with Superformance cars.

[DANGER]

John,

Did you remove the bracket for that shot? Or just have on laying around?

[Silverback51]

The early SPF cars had an issue with the rear end housing being mounted to low in the frame. This caused the band on the inner drivers side CV boot to hit the frame and rip off.

I pulled the bracket off and had a friend plug weld the existing holes, and then I machined new ones .50 inches higher. This results in a slight tilt to the rear end housing, but it has not caused any problems to date. And I now have .25+ inches clearance between the frame and the band on the CV boot.

While I had it off, I figured I would take a picture of it in case I needed it for future reference.

[scootter]

That is the bracket. I will try to take some pictures in place.

I purchased longer bolts hoping to keep the threads out further from the frame mount.

Might be easier to have less HP!

Scott

[CWizard]

Originally Posted by scootter

It is the bracket that holds the back of the differential to the frame. It is bolted to the back with two bolts then goes up on top of the frame. I have a temporary bolt in there now and hopefully changing it tomorrow. I will take some pics of the bracket. The one that was in there didn't have a long enough shoulder to go all the way through the bracket. It snapped right at the end of the threads. The new bolt has a longer shoulder to go all the way through then i can put a washer and a distorted thread lock nut on it.


Scott

Thanks for the clarification. And good catch!

[scootter]

Sorry for no posting pics yet. I must have got food poisoning Saturday. I have been sick since then. The doctor said IDK!

Scott

[Randy Rosenberg]

That sucks. Hope you feel better soon...

[PANAVIA]

Put those other pictures up you spoke of !

[scootter]

Finally uploaded the picks. Not the easiest place to take pictures, but I think you can visualize. BTW, no comments on how dirty the bottom is. I drive the car!!!!!!

Location of bracket with temporary bolt installed. You can see it was way to short.;

Bottom View, with temp bolt;

Top View, with temp bolt;

Side View looking from drivers side with temp bolt installed and new one on top;

Old Bolt Shoulder length, broken bolt;

New Bolt Length Showing shoulder passing the end of the bracket;

Bolts, bottom one is the old broken one, middle one is the temporary and top is the new one;

There you have it!

[tkb289]

Scott,

Great photos and good catch by the wife to get you to take a look

Going with the longer bolts good idea, the shoulder of the bolt will take the load better than the threaded part. Looks like once the new bolt is in, it will extend well past the end of the nut, so there is thread should the nut start to back off and loosen up.

[Woodz428]

Doesn't look too dirty underneath. I can recall a pic from one SPF owner that claimed they "meticulously" maintained their car and it had corrosion on the rotors as well as other parts and a broken shock bolt. I believe he is selling some hyped shock mounts now. By his standards your is pristine or maybe "museum quality" a term he also used when selling a crappy bondo buggy to a "friend",LOL.

[PANAVIA]

Yup that looks like the 8.8 mounts.

So every time you take slack on and off the driveline that bolt gets some action.

Same engineering issue as the shock mounts ,using bolts that are long enough, as opposed to bolts that are the proper length.

http://www.mcmaster.com/?m=true

Is your friend


Steve

[scootter]

Mc Master's is. I have ordered my stainless bolt's, lead hammer and all kinds of other stuff there.
Problem now is that I have 4 bolts and 24 oblong nuts left over!!. If anyone wants longer bolt let me know. I only have about $50 invested ( not from Mc Masters just al the different places and bolts I bought to get by) in changing one freakin bolt. I will be keeping one spare.
Scott

[mark_n2]

What size and length is the correct bolt. I pick one up and install before it becomes an issue...