I'm having trouble with CV joint bolts in the outer CVs of my mostly-track 944T, and I've seen 911's experience the same problem.

In past years I've found the bolts loose during pre-track inspections. Last year one let go completely. Apparently once a few bolts loosen up sufficiently, there's enough play that the banging forces eventually shears them off. Fortunately I was off track at the time.

After that incident, I drilled the bolt heads and safety wired them. Well they didn't loosen, but at the last event of last season, I started hearing a clunking noise. Turns out 3 bolts on each of the outer CVs sheared. The safety wire is still intact and tight. These are factory bolts, cleaned of grease and properly torqued.

Anyone else experience this and have a solution? I thought safety wiring would be the ultimate solution. Perhaps these bolts were just fatigued from prior use?

Jon.

 

Loctite

 

New bolts too.

 

I second Larry, new bolts. They are stretch bolts and reuse changes the clamping force and lifespan. After you install the CV in place, blow the holes and threads in the flange clean with some brake kleen and then use Green locktite or wire after setting to torque. Green is a wicking fluid and goes on after the fastener is set. This keep the locking agent from changing the torque value. Most are dry values.

 

Good advice here, Jon;

I have NEVER had a CV bolt come loose. On my own car, I have never replaced one either. They are all still the originals (except for a couple that stripped, replaced with used ones), and have been in and out NUMEROUS times. Part of their longevity may be the manifest stress of my Raging 147HP. The only time I replace them on any of my track client's cars is if I get new axles and the bolts come in the box.

I have never used a torque wrench on one yet. I tighten them by feel, which I'm sure ends up being far tighter than the factory setting. I've never snapped one either.

New bolts are not a bad idea, of course, and I wouldn't chastise anyone for requiring them. I think one of the real keys is as Kurt said; clean the threads. I also clean up the outsides after installation, and paint mark them for easy visual inspection.

I'd be glad to tighten your bolts for you sometime. Going to NNJR Mid O this Spring?

 

Thanks for the advice. New bolts, clean threads, torque and safety wire. If that doesn't hold 'em... ?

John - no Mid-O for me.
Our Schattenbaum Region track schedule opens later today (once I update the website).

Jon.

 

Besides using new bolts I always fully clean the stub axle flanges and threads and use loctite 271 (red=high strength).

Norm

 

The turbo is significantly harder on the bolts than John H' na car.

Safety wire will keep a fastener from backing all the way out; but has to be installed exactly correct to actually keep a fastener from losing clamping force. Even then ... I doubt any of us can get into the cv adequately to get the safety wire that well strung. Loctite is better; IF you can get clean surfaces.

For the turbo on the track: the new bolts, correct torque, paint marks, and frequent inspection.

BTW, most guys are too picky about torque in some situations. John H' 'overtorquing is the way to go - within limits. 10% above spec is certainly reasonable in this steel on steel application. Or, by feel (me too John).

 

The safety wiring was done properly, wrapping the twisted wire clockwise around the bolt head and daisy chained to the next bolt. Not only is it impossible for them to back out, they can't even turn more than 1/4 - 1/2 turn at most. Looking at them, you would not suspect that three of the bolts had actually broken where the threads enter the stub axle flange. It wasn't until I cut the wires that I found that these bolts were broken. I don't even think paint marks would have helped. That's why I suspect fatigue.