I've got a friend with a '97 coupe that has some thread damage in the rear center carrier section. It's the passenger side upper sway bar bolt that's threaded into the aluminum carrier. I've seen this now on three different C5s; both on the left and right sides. The bolts come out OK, but going back in it's taken me a half hour using anti-sieze and cutting oil to get the bolts back in without damaging the threads.

Apparently whoever took this bolt out last time didn't take the time to get it back in correctly. When I took to bolt out I pulled whole circles of threads out of the carrier. At least a quarter of the threads are completely gone, and the rest look to have damage to some extent.

So, I have two questions:

1. What causes this problem? I've never seen both sides suffer this on the same car. It's almost like the fasteners are torqued right to the edge of what the aluminum can take, from GM.

2. I think I'm going to have to helicoil this fastener, so can you tell me what the size is of the fastener?

TIA, and have a good one,
Mike

 

Sounds like someone either cross-threaded or over-tightened with an air wrench. I was at an exhaust shop once and asked them to use a torque wrench on my sway - the tech told me they didn't have any. I told him to just snug it and I'd torque it at home.

Don't know the size of the bolt but a thread gauge can fix that easily. In a pinch, I take one with me and match it at the parts store.

Best of luck in the fix.

 

Patches,

I'd believe that, except that I've seen it now on multiple C5s on different sides. In at least two cases (my car being one of them), I believe they had never been off the car.

And, considering how tight I've seen things be when coming off for the first time, I do agree they're probably overtightened, but I think it's happening at the factory.

Yeah, as far as running through the thread pitch exercise goes, I can do that, I was just hoping someone would know.

Thanks anyway, and have a good one,
Mike

 

When I changed my exhaust, I had to drop the swaybar.

So I took out these bolts, swung the bar down, changed the exhaust.

When I got the swaybar back up, and started the bolts, one went in fine.

The other one on the passenger side went in with way too much torque to get it clamped down. I hope the rear carrier hole isn't stripped if I have to take it off again, but it did tighten down tight.

So mine is messed up also.

 

This actually happens quite often and we have seen several that have happened on cars that the bolts have never been removed since original assembly. Our bust guess is that there was dirt or stray cuttings in the hole when they installed the bolt at the factory, causing the threads to gall.

Here is the most common fix, as you may know, that hole is drilled much deeper into the x-member than the sway bar bolt penetrates, so you can chase threads deeper into the x-member and simpy get a longer bolt with the same thread pitch and diameter. On race cars that we know the sway bar will be instlled and removed several times, we install studs into x-member and simply use nuts, like the lower connection uses. I think that they are 12mm x 1.75 but I'm not sure as I'm at home.

 

I bought an '04 vette with 5k miles on it. I know for a fact I was the first person to remove the rear upper sway bolts since they were installed at the factory.

I had the exact same problem mentioned here, I could easily install the driver's side but for the life of me couldn't get the pass. side bolt to go back correctly. I could barely get it started!

Frustrated because I didn't want to strip the threads on my brand new baby I decided, instead of just forcing the bolt back in I'd get a tap and re-tap the hole.

I lucked out! At Pep Boys they had a device to measure the bolt thread pitch etc. but didn't have a tap. I went to two other auto parts stores striking out at each. Finally I headed to Sears and they had it!



This worked perfectly! I really only had to tap a very short distance into the hole, like the first few threads. I sprayed WD-40 into the hole before and after tapping. Then I blew compressed air into the hole to hopefully clean it out afterward.

Once tapped the bolt hand-threaded in perfectly. So, I removed it, put some anti-seize on it, threaded it back in, torqued it to 49'-lbs. and was done!

I've removed it once since, to install z06 Ti's. It removed normally and threaded back in without any difficulty.

The tap I bought was: M12-1.75 from Sears. Cost: $4.99. Well worth the purchase ahead of time if you are thinking about doing a rear swaybar upgrade. No sense screwing up the threads if you don't have too!

..rickko..

 

Good advice, Rickko. I usually tap damaged threads first when I encounter them and it fixes 95% of them. I bought a metric tap and die set when I first bought this car realizing it was a machine full of tapped aluminum holes. That set has come in handy on my car on for a few of my buddies.

One quick note - the torque value for the swaybar upper clamp bolt is 49 lb. ft. It's 70 lb. ft. for the lower clamp nut.

 

Oops! You are right!

Thanks for correcting that. I'm going to go back and edit that into my post. I'm sorry I didn't catch that.

I hate making mistakes like that.

..

 

Amazing - so many have had this problem and this is the first I've seen it posted!
I had the same story as rickko - good save!

 

I whish I would have seen this last weekend when I put my Corsa's on :o

Thanks for the info, I'm looking to upgrade the anti-sway bars sometime soon so I'll get a tap when I do

 

Spit on it. Works every time.

 

Aw, Lemans, we're not talking about THAT!

 

Just to close the loop, we ended up heli-coiling the damaged threads. That bolt is indeed a 12 x 1.75 mm, and once we drilled out the damaged threads sufficiently, we got it tapped and the heli-coil installed with no problem.

Oh, and later in the day I installed an exhaust system on a '04 coupe, no problems whatsoever.

Have a good one,
Mike

 

Good!