Front upper control arm hole stripped
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Joined: Jul 2018
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From: Huntington Beach
Front upper control arm hole stripped
I’m doing some suspension work on my 2003 C5Z. As I was torquing the upper control arm bolts one gave away. I was initially thinking I would use a helicoil repair. However looking closer it looks like the rear most hole has been repaired already. I noticed a washer-like silver appearance and after looking closer at the other side it seems clear some type of insert has used to repair the thread. I’m curious if anyone else has ran into this concern and how they resolved it.
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From: Huntington Beach
I am completely rebuilding the suspension to race the car. I was in the process of refitting the upper with the LCA supported by a floor jack. My intention was to use studs when it was aligned and reinstalling the OEM bolts was only temporary. I’ve since decided the studs will go in now...
I am considering using a helicoil repair, and that would leave me the possibility of using a nutsert style fix if needed. I’m also not crazy about having the nutsert shoulder in place with shims on top though I’m likely overthink thinking things. I’m also not sure there’s room for a nutsert installation tool given the proximity to the upper shock mount. Although I know I could create something to install it without the tool.
I noticed, but did not register, what appears to be a previous repair during tear down and it looks like a nutsert to me. I only recently bought the car so I do not know it’s history except the previous owner was autocrossing it in stock configuration.
I am curious to know what GM would spec for the repair, although recalling some other OEM “fixes” for suspension issues that might not be the best option. I cannot tell if there is any backing plate and there is no OEM thread inserts. I’ve attached a pic of what appears to be a previous repair with a nutsert type fastener.
I am considering using a helicoil repair, and that would leave me the possibility of using a nutsert style fix if needed. I’m also not crazy about having the nutsert shoulder in place with shims on top though I’m likely overthink thinking things. I’m also not sure there’s room for a nutsert installation tool given the proximity to the upper shock mount. Although I know I could create something to install it without the tool.
I noticed, but did not register, what appears to be a previous repair during tear down and it looks like a nutsert to me. I only recently bought the car so I do not know it’s history except the previous owner was autocrossing it in stock configuration.
I am curious to know what GM would spec for the repair, although recalling some other OEM “fixes” for suspension issues that might not be the best option. I cannot tell if there is any backing plate and there is no OEM thread inserts. I’ve attached a pic of what appears to be a previous repair with a nutsert type fastener.
Last edited by SpedeRacer; Apr 20, 2019 at 06:20 AM.
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From: Huntington Beach
Well they are two different holes. One was previously repaired and the shoulder could be a problem since I will be setting the front end geometry off the upper control arm now. I am not sure what that is or how big a hole is hiding under that shoulder that is visible. SO I am a little shy to start drilling on it. If I knew it was all shoulder and maybe 12mm wide that might not be too bad to deal with. Then I have the new one (the hole without a repair) to figure out. I tended to agree with you about using a helicoil. This would seem to be a lateral load and not anything trying to pull the stud (or bolt) out of the hole. But everyone wants to go with a nutcert or similar. I might be ok using a timcert but I have not decided yet. I would really like to hear from a GM engineer or someone who has dealt with this situation and then raced the car.
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From: Huntington Beach
I am also trying to determine what exactly is there in the frame material to accept the threads. Is it just thicker frame material? Something on the backside? Or inserted? It looks a bit like there is something sitting in that hole. And there is an obvious rectangular pattern in that area, though I do not see anything similar in the area of the repaired hole.
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From: Green Oak Township, Michigan
I see that rectangular pattern. Disc it off and see if that pattern is a weld seam. I dont see how they could have welded a boss on the inside, but I guess anything is possible. If theres a boss on the inside, you could always just drill and tap for the next size bolt. Then just drill clearance for the new bolt in your control arm. This would eliminate the insert all together. It would mess up your stud idea though.
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From: Green Oak Township, Michigan
yea, I see what you mean. You have to make an insert work then. This is pretty radical... but then I was in too and die. A good welder could burr out a rectangular hole and fit a steel,, half inch thick...insert in the hole and weld it in place. Transfer punch the hole in the insert before it is welded in. Then you can drill and tap the hole in the insert on a Bridgeport or a drill press. Like I said, this would be a last resort. I hope that you can get a Helicoil or some other insert to work. I hate to even mention this, because the average guy just doesnt have the ability to do it. A Racecar Fabrication shop in your area could do this.. They would have a plasma cutter and all the equipment to do this. anyway,, Good Luck in your venture.
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From: Huntington Beach
For those following, I chose a key insert because I as not sure how much material was there to use a (9.4mm) timesert. In the end I likely could have used either after drilling for the key insert. I had a little trouble working close to the shock tower support so I had to modify the tools I used (driving the 14mm tap and using the tool to drive down the four key locks). But in the end I am very please with the results and do not see any problems going forward.