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Ok, so the rear upper shock mount on my C5Z, the threaded hole that bolts the shock mounting plate to the frame has stripped out. Normally it is an M8 x 1.25mm pitch thread. Has anyone had any luck just drilling and tapping to the next side up (say 3/8"-16).... I guess a helicoil could work, but you still have to drill and tap, so its more work. I know this has happened on more than a few cars, just looking for someone who has done the repair and what you did.
I did the same thing. Here’s what I did after a great deal of research and rumination-
I first tried to tap the hole to the next larger size, as you suggested. I was not able to have enough working room to tap it out with the tap and die set that I own. So here’s what I ended up doing:
I drilled the hole out to clean it up and make it smooth, then used a hole saw to drill a 2” hole in the fiberglass rear tray right above the shock mounting point. I bought a high quality m8 x 1.25 x 25mm grade 10.9 bolt and nut. I ran the bolt from below and secured the nut from above through the 2” hole. I bought a plastic/rubber lightweight plug to fit in the hole that I drilled in the fiberglass tray. It looks factory to be honest, if you were to pull up the carpet and actually look at it. It’s hidden under the carpet and no one would ever actually see it unless they looked.
Good luck- it’s not too big a deal. Here’s a photo or the plug in the hole in the rear tray, under the carpet.
I was not convinced a helicoil or riv-nut would be strong enough. A proper grade 10.9 bolt and nut certainly are at least as strong as the original set up.
Last edited by wkcarson; Jul 18, 2022 at 02:43 AM.
Great solution - I just striped mine yesterday and spent my night thinking about this instead of sleeping......so one question - did you just eye-ball the location for the hole or is there a better way to do it? My stripped bolt is the one towards the front of the car. is that the one you stripped also? Just wondering if I can use your photo and be lined up with the right bolt hole.
Great solution - I just striped mine yesterday and spent my night thinking about this instead of sleeping......so one question - did you just eye-ball the location for the hole or is there a better way to do it? My stripped bolt is the one towards the front of the car. is that the one you stripped also? Just wondering if I can use your photo and be lined up with the right bolt hole.
The OP has not been online since March. I would definitely favor the rivet-nut path instead of cutting a hole in the car.
Last edited by lucky131969; Sep 18, 2024 at 08:55 AM.
stripped rear upper shock mount frame hole
