Need help with bolt size :(

measure the width of the bolt hole and go find a bolt at the hardware store as mentioned above that's close, in SAE and metric, in all available thread pitches. Return the ones that don't fit. This is pretty easy stuff. Especially since there is a junk yard near you and you now know that your truck has a half ton frame.

Just had to buy a couple. My truck is a 90. M10-1.5 is the thread size. First post I better be right.

509OBS said:

Just had to buy a couple. My truck is a 90. M10-1.5 is the thread size. First post I better be right.

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You’re the man!

I still think that with a conventional head size there may be clearance issues. IIRC, my impact sockets won’t fit, and I have to use my chrome sockets to get to the original style front bolts.

Forgot to add mine is a C1500.

As a person that is always on the lookout for a reason to buy more tools, this feels like a good reason to buy a nice set of metric taps

Ok, the bolt size for the front sway bar bushing brackets is M10-1.25x25 for future reference.

Found this while searching for replacements, figured might as well add to it. On my 97 K1500 ExtCab Z71 the stock sway bar mount bolts are M10-1.5 x 30mm, class 10.9. I ended up replacing with Socket Head Cap Screws (class 12.9) from Axe Hardware.




You'll need a short 8mm hex bit or some decent swivels/wobbles to get them in. I was able to do it with the truck on jack stands using a Capri 3/8 drive hex bit and a standard Craftsman (old style) ratchet, but it was really tight.

It's really tight because you didn't use the correct hardware. There always a good chance an impact socket will have clearance issues on small hardware. A ten millimeter bolt with a 12 or 13 millimeter head is hand tightened with a 3/8 or 1/4 drive regular or deep socket. When those grade 8 Allen head fill with dirt and rust won't that be fun getting them out.

@mdnky is correct. The bolt size is M10 x 1.5 x 30 (GM part no. 15592554, discontinued). I found OEM bolts on eBay and paid an arm and a leg for them.

GoToGuy said:

It's really tight because you didn't use the correct hardware. There always a good chance an impact socket will have clearance issues on small hardware. A ten millimeter bolt with a 12 or 13 millimeter head is hand tightened with a 3/8 or 1/4 drive regular or deep socket. When those grade 8 Allen head fill with dirt and rust won't that be fun getting them out.

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Post was specifically made to mainly highlight the proper size, more than what I bought. Well aware the ones I used are not the 'correct hardware', however I prefer cap screws in situations with limited space. I'm also unwilling to pay the ridiculous amount they want for the originals, nor do I have the time to waste waiting for them to ship.

I use cap screws on my Jeep (which sees heavy off-road use) and I have never had an issue with dirt or grim in the heads. In fact Jeep uses Allen head screws all over the vehicle (transmission, t-case, diffs, etc.), as do a lot of other manufacturers and OEMs. If anything does get in there, you can clean it out with a pick and some PB blaster in a few seconds. Besides...they're going to get a thick coat of FluidFilm soon as well...doubt rust will be an issue.

The fitment part was just included as a caution/extra info, in case someone else tries it. I didn't want to use any swivels or wobbles to install (they would make it easier), yet I was still able to do it. Just used a plain old Craftsman 3/8 drive hand ratchet. Definitely didn't use an impact socket either, nor would they fit there (standard impact sockets).

The cap screws I used are metric class 12.9, which is significantly stronger than a standard grade 8 bolt. The factory bolts are actually class 10.9, which is roughly the equivalent to (slightly stronger actually) than a grade 8 bolt.