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GM drum hub failure

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Randy 67EC

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Discussion starter · #1 ·
Well, it looks like 43 year old parts don't like autocrossing. I had a right hub fail right at the end of my first (and only) run. Took quite a bit to get the car on the trailer, will be getting a winch for sure now. Luckily the disc brakes held the wheel in place enough. The caliper pins bent for sure and possibly the abutment as well. Rotor was chewed up some from contact with the abutment. I will know more once I get them off and the drivers side off so I can compare them. Good to keep an eye on stuff like this, even though I couldn't find any signs of cracks beforehand.

Here are a couple picts of the carnage
Hub
Image


Hub now a 2-piece design
Image

Image
 
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#2 ·
Wow randy. I am glad you and your camino are ok. I have never seen that on a street car. I have seen that on old street stock circle track cars though, and broken axles too. What are your plans for repair/replacement?
 
Discussion starter · #3 ·
Short term I will be using another stock hub. I would like to upgrade to some billet hubs like Kore3 has, money is a bit tight right now. Hopefully I don't have to replace too much of the brake parts.
 
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#4 ·
Using wheel spacers or wheels with incorrect geometry?
 
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#5 ·
Wow. Breaking parts like that means you were driving it right! :thumbsup: Your pics make me glad I coughed up the extra cash for the billet hubs.
 
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Discussion starter · #7 ·
Schurkey said:
Using wheel spacers or wheels with incorrect geometry?
Click to expand...
No wheel spacers at all, wheels are 17x9 with 5" backspace with Kumho V710 tires. Autocrossing was probably putting more strain on the hub than it was willing to put up with after 43 years.
 
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Discussion starter · #8 ·
GenPac said:
Wow. Breaking parts like that means you were driving it right! :thumbsup: Your pics make me glad I coughed up the extra cash for the billet hubs.
Click to expand...
I was having fun right up until the failure. Even with just one run, I still managed to be 3rd out of 5 drivers. :D It failed on the last part of the run, just made it across the finish line.
 
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#9 ·
Glad you're ok. I had a LCA failure last year and it makes me realize how old our cars really are but more so in that they just simply aren't designed to take on the abuse we're putting them through. I'm starting to get worried about driving it hard and I do drive mine hard in the canyons. So many weak points like the LCA chassis mounting location, hubs, spindles, LCAs, etc... It's just getting daunting on all the parts I/we should consider reinforcing or replacing. I mean.. where do you stop?

I'm thinking of tossing-in the Pro-Touring towel and just dumping this thing on bags, cruise it and be done with it. I don't like the thought in the back of my head every time I head into a canyon turn thinking something will break and throw me off the edge :(
 
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Discussion starter · #10 ·
No need to give up on your car. There are things you can do to help ward off problems, whether it is replacing parts or reinforcing them. Plenty of ideas here and on other sites. You just need to be in the habit of examining the parts on a regular basis to try and catch problems before they happen. The hub never gave me any warnings, just gave up. There is always a risk involved with any car, no reason to stop living the dream.
 
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#12 ·
Yikes. Luckily it went out at the autox. Now I'm glad my drum hubs were long gone and not an option when doing my brake swap. The Kore3 hubs will also drop some weight off the front. Mine have been running good so far. Glad nothing got torn up bad and you were safe. Had you trailered the car to the autox?
 
Discussion starter · #15 ·
Yep, I trailered the car to the event, just in case. Glad I did.

The studs are 3" long 1/2" ARP with larger knurls. I will be going with another drum hub for now. The hub that broke is different than the one on the other side. The backside of the flange has some scalloped areas (see the photos) while the other is smooth on that side and a little thicker as well. We will be magnafluxing the hubs to be sure.

I am building a Camaro for dedicated autocross duty, to be more competitive at divisional and national levels. The El Camino does well at a local level, with more work it could be more competitive, but I'm not going to cut it up just to run bigger wheels/tires and a cage. Don't think the hubs would stand up to big slicks anyways. If I was going to keep running the El Camino, I would get the Kore3 hubs for it. I actually have the El Camino up for sale and even have someone wanted to look at it. Luckily they are understanding and willing to wait until I fix it to come see it.
 
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#16 ·
Randy 67EC said:
I am building a Camaro for dedicated autocross duty, to be more competitive at divisional and national levels. The El Camino does well at a local level, with more work it could be more competitive, but I'm not going to cut it up just to run bigger wheels/tires and a cage.
Click to expand...
Lets see this Camaro!!! I've been seriously considering building a 2nd gen Camaro into a full-prep CP car. Decent 2nd gen bodies are cheap and plentifull enough that I wouldn't feel guilty about cutting it up to meet minimum weight.

On the other hand, for a whole lot less, I could just buy a Miata and be in a nationally competitive car for less than it would cost to build a CP engine...
 
#17 ·
derek69ss said:
on the other hand, for a whole lot less, i could just buy a miata and be in a nationally competitive car for less than it would cost to build a cp engine...
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+1
 
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Discussion starter · #18 ·
Derek69SS said:
Lets see this Camaro!!! I've been seriously considering building a 2nd gen Camaro into a full-prep CP car. Decent 2nd gen bodies are cheap and plentifull enough that I wouldn't feel guilty about cutting it up to meet minimum weight.

On the other hand, for a whole lot less, I could just buy a Miata and be in a nationally competitive car for less than it would cost to build a CP engine...
Click to expand...
Ah yea, but you haven't been to an epic CP party at Nationals. Plus there are too many Miatas anyways. You actually don't need a lot of engine, mild motors do quite well, suspension/wheels/tires will get you farther.

Here are some initial picts of my car over on NastyZ28.
http://www.nastyz28.com/forum/showthread.php?t=184672

And here's another one being built by another member.
http://nastyz28.com/forum/showthread.php?t=131539
 
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#19 ·
Randy,
I have seen similar failures on crankshaft snouts caused by the timing gear not having a proper radius and not seating properly against the step on the crankshaft. When you get your replacement hub, before you put the studs in it, glass bead it then spray or brush some machinist die on it. Then place it into the back of the wheel and spin it while putting pressure against the wheel. See if the wheel is contacting the flat area on the hub properly. Also, the step in the middle of the hub should be a "snug" fit on the wheel to keep it centered. They studs should not be keeping the wheel centered, the hub should.

Then again, it might just have had enough after 40 years :)
 
Discussion starter · #20 · (Edited)
Thanks for the info Bill. I have the replacement hub now.

We did find out more about the broken hub. There was a void in the casting right along where it broke. You can kinda see it in these pictures, sorry my camera didn't take better shots. It's the area I circled on each shot, kinda the darker area.

Image

Image
 
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Randy 67EC
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