I starting hearing a metallic clanging noise coming from the left front side of my 93 S10 Blazer 4x4, when going over bumps or rough road. I noticed the steering seemed a little loose, so my first thought was "tie rod ends", but they aren't that bad, and the high-pitched rattling didn't seem consistent with tie rod problems.

What I did find blew my mind. All 6 bolts that hold the CV half shaft flange to the transfer case were gone and the CV was hanging loose, ratting against the strut when going over bumps.

I have tried, in vain, to find out what kind of bolts I need. Only thing I can find is a set of 4 for an older full-size model. I have a thread gauge, but only in inches, and I don't know if these bolts are supposed to be metric or imperial.

Also, I dont know if the splines at the end of the shaft are damaged, but I am able (with moderate effort) to push it back in. The flange looks okay, and the boot is undamaged, but will I have to top something off after getting the axle back in?

 

Disclaimer: I've never owned a 1st gen Blazer, and I have no specific memory of working on one or dealing with parts for one. I'm offering general information from years of experience as a mechanic and parts man(ager).

The bolts should be the same on the right side. I'd pull one of those and take it to a good hardware store and match it up. The head style is critical. Grade (SAE) or class (metric) is important. You can generally go up on grade or class, but never go down.

Also check the splined section. If there is an unfilled groove, you're probably missing a snap ring.

Tightening torque is fairly critical on those bolts. They can work loose if they aren't tight enough (obviously). Use a good torque wrench and get them properly tightened.

You need to at least top up the diff lube. This might be a good opportunity to change the diff lube. It's supposed to be changed every 30,000 miles, but almost nobody bothers to change it.

 

I pulled a bolt from the right size, it is metric (10.9), 15mm head, about an inch long, with a "C" on it, whatever that means. The local advance auto had some with matching thread, but about twice the length, fully threaded, and $3 per pack of 2.

I'm going to check ace hardware in the morning. I noticed that the bolts at advance were marked grade 10, and not 10.9. Also, is it imperative that the bolt has the unthreaded section at the top?

 

Of course, it has to be the one a that 15mm wrench fits?

That's a 10mm ANSI/ISO spec bolt, or,because of the unthreaded shank,maybe DIN spec with a "standard undersized" hex head. If the thread pitch is 1.5, it's probably ANSI. If it has fine threads, 1.0 pitch, it's probably DIN undersized head.

All the "normal" Ace hardware stores around here carry standard DIN sizes, so a hex head M10 bolt will have a 17mm head. Those probably won't fit or your wrench won't fit.

You could get socket cap bolts at your local Ace Hardware or Home Depot (class 12.9, uses 8mm allen wrench).

You could also get a class 10.9 or 12.9 bolt from an auto parts store that is JIS specifications (might say "for Japanese or Asian cars" on the package). M10 bolts in JIS specs have a 14mm hex head, which should fit where your ANSI spec bolts fit.

As for the unthreaded shank, it shouldn't matter. Harder, higher class/grade bolts have specifications for the minimum length of the threaded part of the bolt. It differs some from standard organization to another. IIRC, DIN standards call for less threads, more shank than ANSI/ISO. If the engineer who designed that joint and bolt selection used the shank as a locating pin (in which case that engineer is an idiot) then it might matter. If the bolt provides clamping force only, which is what bolts are only supposed to do, then it won't matter.

 

Took some pictures and measurements. The bolt/screw is 30mm long (including head), 25mm long shank with a threaded portion about 20mm long. I found these online $7.25 - M10 X 1.5 X 25 Metric Hex Bolt / Cap Screw 10.9 Qty (10) [MCS1025CFZ109] : NutsandBolts.com

But I'm not sure if the one I have is coarse or fine.

EDIT: Probably coarse; also, I stumbled across this NSN 5306-01-369-8191 which seems to match my specs pretty well, including head size: http://www.parttarget.com/5306-01-36...0-5E865CCC4C9F

 

I can help you with identifying what you have. That's definitely coarse threads (1.5mm thread pitch).

From the picture, you have a M10-1.5 x 25mm hex cap bolt in material class 10.9 that meets ANSI B18.2.3.1m specs.

In this application, you want material class 10.9 or higher. Don't go with 8.8 (or lower) as those will be less strong and could potentially break.

Other bolts you should be able to use in the same location:

• M10-1.5 x 25mm hex socket head cap bolt in material class 10.9 (or higher) that meets DIN 921 specs. This one uses an 8mm allen wrench. Ace Hardware stores and Home Depot stores carry these, but you can't always find every size online on their web sites. Walk into a store and look. This is the bolt I would be looking for as a replacement/substitute, if the ANSI spec bolt isn't easily obtainable.
• M10-1.5 x 25mm hex socket head cap bolt in material class 10.9 (or higher) that meets JIS B1180 specifications. These bolts have a hex head that fits 14mm wrenches. These are available at many auto parts stores, and come in packages that say "For Japanese or Asian cars." O'reilly might have it. They list Dorman 005420bp as a 20mm long version, and Dorman 005440bp as a 40mm long version. I don't see any on the web site between those sizes, but I think if you go in the store, you might find them.

Other bolts that might have issues in this application.

• M10-1.5 x 25mm hex socket head cap bolt in material class 10.9 (or higher) that meets DIN 931 or DIN 933 specs. These are widely available at hardware stores and home improvement stores (Ace Hardware, Home Depot, Lowes, etc.). It's also available at auto parts stores, look for Dorman #980-525 or an equivalent of that. These have 17mm hex heads and might have clearance issues with the head of the bolt or the wrench or socket you have to use to tighten them properly in this application. If they fit and you can get a socket wrench on them and tighten them all the way, they will work. I'm skeptical that the wrench or socket will clear everything. You could test one and see.
• M10-1.5 x 25mm hex socket head cap bolt in material class 10.9 (or higher) that meets DIN 6921 specs. These are flanged bolts with a nominal 23mm flange ("integrated washer"). If the OD of your 15mm socket is under 23mm, and your socket fits in the space around the heads of the bolts you have, these will work. Otherwise, the flanges on these might not clear. You'd have to test one to see.
• M10-1.5 x 25mm hex socket head cap bolt in material class 10.9 (or higher) that meets JIS B1189 specs. These are flanged bolts with a nominal 21mm flange ("integrated washer"). They use a 13mm wrench or socket. Again, there could be a clearance issue with the flange, but this one is smaller than the DIN spec flanged bolts. These can also be found at many auto parts stores with the label "Fits Japanese and Asian cars."

As to the links you had, the first one was a "mystery bolt" with no indication which DIN, ANSI or JIS specification applied, and key dimensions missing from the description. Without that info, who knows if it will fit. The second was for a flanged DIN 6921 spec bolt. That one has a 23mm flange on it (22.3 minimum diameter, 23.0mm max diameter), and it might have clearance issues in this application.

Also, if you go with a flanged bolt, for this application, you need a smooth (not serrated) flange.

Oh, and if you want the full specs and dimensions for any of the specifications I mentioned, go to Google, look for the spec ("JIS B1180" for example), and look at the images. Some bolt manufacturer will have the specs as a graphic on their website.

 

Thanks Racer_X! One thing I love about this forum, is knowledgeable people and technical details. Where I live, all those I propose questions to respond with basically "eh, might work" or "go to a junkyard". And yes, while I know of a particular, almost identical, Blazer in a nearby junkyard, I'd like to know just what I'm dealing with. Plus, I think someone already got the front axles off of it.

 

Okay I found these from Trinity Logistics Group:

Trinity M10 - 1.5 X 25MM ANSI HEX HEAD CAP SCREW 10.9 ZNYEL Trinity Hardware Headquarters


Their catalog lists them in a couple different finishes, but their online store only lists the zinc yellow one. I have to create an account (which is currently awaiting approval) and according to fasternersclearinghouse.com, they have a minimum $25 order. That's not too bad, but I dread seeing the shipping cost.

 

OE number is 11509419 according to parts.nalleygmc.com. Your local GM dealer should have them on hand, but they'll run you close to $4 each unless the counter guy knows you and is willing to cut you a deal.

As you have found, it is a M10X1.5X25 grade 10.9 bolt. You can also find them at most farm supply stores or tractor dealerships in bulk. I know for a fact that the John Deere dealer near me has bins of these exact bolts as I recently had to buy lower grade M10x1.5x25 bolts for a bracket I was fabricating to put on a new tractor of ours and saw the 10.9 bolts in the next bin over.

The unthreaded portion of the bolt serves no purpose in this application so don't let that worry you when scoping out your options.

 

When you got those at the tractor dealer, were they ANSI B18.2.3.1m heads? Those use a 15mm wrench. Or were they for a 17mm wrench (DIN 931/933)? or for a 14mm wrench (JIS B1180)?

I haven't checked tractor dealers, and there are several new tractor dealers that have popped up near me.