George A

Has anyone had their stub axel break? I broke mine in last weekends DE. The strange part is that I broke the wheel bearing about a month ago and had everything replaced (driveshaft and wheel bearing). Anyway, coming out of the fastest turn, I felt as if I had a flat. As I rolled into the pits, the car suddenly came to a stop, like I had the brakes on. When I put it in gear and let go of the clutch, nothing happened (I don't have a LSD). When I went back and looked at the wheel, it was only being held on by the caliper. The part of the drive shaft that goes through the carrier (the part with the teeth) was missing, including the nut.

What do you think could have caused this? Too much or too little torque on the nut? I'm baffled as it was a brand new driveshaft.

I guess I'll also post this in the Racing forum to see if I get any more opinions.

George

johnfm

I think there waws one of these a while back. Check the archives.

chris walrod

Can you post pics of the damaged stub axle? Maybe over torqued at the time of your bearing install?

Please post some pics!!

This is one item that I will have crack checked if I ever remove it for wheel bearing R&R, or otherwise..

Sorry to hear of your DNF..

George A

Chris,

I'll try to take some pics but I dropped the car off at the shop on my way home from the track. I'll see if I can swing by there sometime in the next couple of days.

The stub axel is not damaged, it's missing. Basically everything to the outside of the cv joint is missing, sheered off. It's a one piece deal, unlike the inside, in which you can replace the cv joint. It's part of the driveshaft, unlike previous models. It's a pretty expensive part, I think cost was around $450.

I had the whole thing (driveshaft and wheel bearing) replaced last month, not just the wheel bearings. One of the guys at the track thought that the nut wasn't torqued enough, which caused some banging, which in turn caused it to sheer off.

George

Ben in Plano, TX

Here's a picture for reference.

George A

Thanks Ben. So, basically, everything to the left of the cv joint housing in the illustration, is missing. I'm just lucky I made it back to the pits without the wheel falling off.

George

Greg Fishman

George,
I have not heard of that happening. I take it you didn't have a major OTE.
I would bet on the nut either untorquing itself or not being installed/torqued correctly to begin with. I posted a while ago about my front hub coming loose and recommended everyone to check it on their own occasionally. I had to replace the hub (part that holds the wheel studs) because the center nut had worked its way loose destroyed the wheel bearing as well.

George A

Greg,

I got extremely lucky, no OTE whatsoever, but it was a handful. I didn't even block the track, I made it to the pit lane. It took over an hour just to load the car onto the trailer from the pit lane. I can imagine all the people that would have been pissed off if I had stopped the track for an hour.

I remember your post about checking the center nut, and believe it or not, that's part of the reason I don't use center caps. I like to visually inspect it. I guess visually is not good enough. I also figured since it was just put on, I would not have to worry about it for a while. I guess I was wrong. I guess I'll check from now on. Got lucky once, don't want to chance it again.

George

Greg Fishman

George,
I meant you didn't have a major OTE that could have caused the problem. I am sure if it was a big enough OTE to break the stub axle it would have damaged a bunch of other stuff along the way.

When we did the axles on my car this spring we re-torqued them after a session or two. I was able to tighten them just slightly. Not the same thing but kind of the same principle.

Ben in Plano, TX

George

I didn't watch the car loading fun but why did it take an hour to load it onto the trailer?

And what has the shop had to say about it?

Ben

Stuttgart

The 993 cupcars have a stub axle (for the center locks) that screws onto the axle in place of the regular nut on the street cars. But it also has a cage that slides over the stub axle onto the nut portion, and engages with part "7" in the diagram above. This keeps the stub axle from backing out, does the street 993 have this cage? If so I don't see how the nut could back off the axle. I've broken two cv axles just inside of the outer cv joint, but never outside the outer cv. If I recall the torque spec for the stub axle on the 993 cup is around 300ft-lbs, so i would suspect that it is similar for the axle wheel nut on a street 993. Does your shop have the requisite torque wrench? I would ask, b/c my best guess would be they didn't have it and just cranked their highest powered impact gun up and might have over torqued the axle nut.

George A

Sorry Greg, I misunderstood. No, no OTE, just in a high speed sweeper.

I guess I should re-torque all my axle nuts as I've replaced all the bearings and driveshafts in the past month or two.

George

George A

Phil, I have a feeling you might be right. I believe the torque spect is 325 ft/lbs. Sounds like the cupcars are different.

Ben, have you tried to move a car with a locked wheel? Basically, the rotor jammed into caliper when you tried to move it. We had to put a dolly under the crossmember to lift the right rear off the ground so that we could move it. It took us a while to figure that out.

George

George A

How do you double nut them? Do you use different nuts? The nuts on my car are pretty thick, I'm sure you couldn't double nut them (item 9 in the illustration).

I think I said nuts to many times.

George

tonytaylor

George,

Did you notice anything prior to stub axel breaking? You state in your first post that it felt as if you had a flat at the corner it broke but did you notice anything prior to this?
Reason for asking is that I've just had a new driveshaft and at last trackday I was getting vibration, like a wheel out of balance, when hot. Blame is being put on a wheel spacer but reading your misfortune has set me thinking about the driveshaft ( again - I uspected it originaly)