Mike Buck

I don't do anything special. Don't even bother cleaning much grease off. Tracking car since 2001.

Bri Bro

I had one set back out (out of several dozen installations) and it was because I was in a rush and didn't follow all the suggestions above. I use new bolts on each installation and make sure all the old loctite is also removed when cleaning the threads of grease. I also check torque before each event and none have been loose to date.

Chris Prack

How's the wheel bearing?

Jeff N.

For those of you retorquing and using loctite - doesn't that break the loctite hold?

Always wondered about that.

Bri Bro

Most of the bolts I check just don't move. I use a needle deflection gauge so it is easy to see if one moves. If one moved on a CV with loctite, I would remove it, clean it up and retorque.

samluke

Its the clamp force on the two flanges that keep the flanges from moving not the bolts themselves. If the flanges start to move the bolts will loosen up. A lubed bolt installation is actually better than dry as the maximum clamp force is generated for the same bolt Torque, and its more consistent.

Its hard to get loctite to work in this application, and if it does, then removal becomes an issue. Bolt stretch is what keeps pressure on the flanges over time, without bolt stretch any relaxation in the bolt joint results in reduction in clamp force.


Correct bolts and grade, correct plates under the bolts, dry flanges, slightly lubed bolts, correct tightening, and re-checking/re-torqueing, wiring for safety, and no issues to date (10+ years and up to 350HP).

I too lost a shaft once but then it occured to me that I had used the torque for an 8.8 bolt not the 10.9, so my fault.

Oddjob

****, I must be either stupid, oblivious, or just plain lucky - I ve never had a CV bolt come loose on me in 15+ years of street/track/racing 944s. Never did anything special with the bolts - no loctite, reuse the old bolts, maybe wipe the threads off, no star pattern torque sequence, etc.

But I bet if I go check the CVs on my cars tomorrow, half of them little f*ckers will be loose!

Musche

IMHO, it's all in the torqueing of the bolts. Kind of like a wheel lugnut or head bolts. Circular-opposite tigtening pattern go around once and then recheck. As long as all bolts are the same the clamp force and is consistent around the circle they shouldn't come loose. Of course this all depends on having a balanced rotating assembly. I usually clean everything up, reuse old bolts, etc. like Oddjob mentions. I will say that as part of my pre-track day prep I look over them and check the torque on a couple of them. Never had one come loose. Probably just jinxed myself.

Jeff N.

Interesting. Good observation on the clamping force. I wonder what I'm doing wrong?

I'm almost wondering if my torque wrench might be reading low and I'm not getting enough clamping force on the joint.....hmmm. A few pounds of error would be significant at a 33lbs spec.

Definitely going to make a specific point to use the cross tightening pattern this time.

kevincnc

I'm a beliver in anti-sieze compound, not loctite on any bolt that has to be torqued to a specific number (on machinery in general.) Otherwise you are not getting the bolt as tight as needed for proper clamping force.

Laust Pedersen

Since the bolts are not press- or slip-fit, the two parts can rotate slightly relative to each other if the clamping pressure is inadequate. That motion stretches and relaxes the bolts slightly and they will eventually work their way out if not otherwise secured.

So there are a number of ways to prevent (reduce chance of) bolt loosening:

1. Use correct torque and Loctite on bolts.
2. Wire the bolt heads.
3. Use clean mating flanges and possibly add some Loctite on the mating surface to ensure high static friction. This adds difficulty to disassembly.
4. Use spiral dowel pins in stead of two of the bolts, by enlarging two of the holes to the appropriate depth. This prevents rotational motion of the mating parts. See picture below how it is done on a Lamborghini Jalpa.
5. Use the same principle from above, but have two small tubes machined to slip-fit on two of the bolts and enlarge the holes to the appropriate depths for light press-fit of the tubes. Unfortunately bolt tolerances require this to be a custom installation sizing the tubes holes to specific bolts.
6. Only use unidirectional torque, meaning never use reverse and never do overrun (car pushes the engine)

When bought my current 951 and drove it home from Omaha, I discovered that 5 of the 6 bolts on one side were finger loose

Laust

samluke

Jeff,

If you have bolts constantly loosening up then something is wrong. Are you using the hardened plates under the bolt heads? If the area under the bolt head relaxes then the torque will back off.

Are you using the correct bolts, type and grade?

I always install mine lubed, and go back two or three times to make sure they don't rotate any more under torque. Wire locking is only a precautionary measure, and is not needed to keep the bolts from backing out.

As you say, you might also want to try a different torque wrench or verify your setting.

wolfenstein

that's what i do

Zero10

For those of you who have had bolts back out or fall out, do you replace the bolts every use, and do you still have the factory metal brackets / washers under the bolts?

Every time I have re-used a CV bolt it has backed out, even after repeated installations with loctite or any other thread locker. New bolt goes in, never falls out on it's own.

I buy bolts from VW since they are cheaper, and they come coated in some kind of blue stuff (really, I don't know what it is, but the whole bolt is light blue). These bolts have never come out on me, always installed dry.

931guru

Race cars with excellent preparation use safety wire.