CV Joint Bolt Torque Question

[arbita1]

The Bentley manual list two different torque ranges dependent on the type of bolt...either hexagon or expansion. How do I know which i have?

[tobluforu]

It really depends on the grade of the bolt, but do you have 4 or 6 bolts, I speculate 6?

[arbita1]

6 per side. Here's a pic.

[tobluforu]

Ok, so I'm going to paste a thread that you should probably read, it's kind of like the bible in regards to cv joints.
Reconstructing Constant Velocity (CV) Joints

[Gunter]

Allen type M8 x 1.25 x 50 mm 12.9 quality bolts requiring 30-33 ft-lbs with a 6 mm Allen key or socket.
Tighten cross-wise, snug first all around and then final torque.
New Schnorr lock washers.
Some have moon plates, some don't.
If you don't use moon plates, the bolts can stick out touching the transmission case, grind a little off.

New bolts are always good especially when the old ones have a worn out hex.

[RWebb]

use the moon plates !

[arbita1]

Why the moon plates? The PET shows the SC doesn't have them.

[DRACO A5OG]

33ft/lb, Just make certain you re-torque them after around 1000 miles. I would also order 6 more as back up they do tend to round out.

Just FYI, I recently dropped my engine/trans. I did not use moon plates or mod washers, just left them the way PAG designed but I did re-torque, what is strange is my past three well known wrenches here did not do either, but because I DIY, I did re-torque them, just to make sure. All were nice and snug

Curious, have any of you that had a wrench work on the CV joints ever had to go back to re-torque?

Jim

[RWebb]

Originally Posted by arbita1

Why the moon plates? The PET shows the SC doesn't have them.

Grady explained it on another thread - you want a certain degree of hardness for the Schnoor washers to bite into

[Walt Fricke]

This contrarian uses neither washers of any kind nor moon plates. The boot caps tend to get squished a bit under the bolt head, but that has never led to loosening of the bolt for me.

I do use 12 point (or, if you wish, triple square) socket head cap screws. These seem to have less tendency to get buggered up than the standard 6 pointers, which is good since I reuse them. Porsche used the 12 pointers for a while, including on 914s.

So there are lots of ways to get things to work well.

[Won]

Before Pelican came along, no moon plates were necessary and not even Schnoor washers. There is a paper published by the maker of Schnoor washer themselves that says used washers do not lose their effectiveness, but of course no one here would listen to it. Like Walt said, there are more than one way to do this properly.

As far as your original question is concerned, it depends on the size and grade of the bolt. Be careful Bentley lists wrong torque spec for one size. Is this for a stock SC's CV bolts?

[Cooper911SC]

I just installed new complete axles on my '81 SC.

M8 bolts 30lbft. No washers or moons...

I torqued and paint marked them.

In the past I ran them the same way. They stayed tight after initial torque.

[RWebb]

Originally Posted by Won

... There is a paper published by the maker of Schnoor washer themselves that says used washers do not lose their effectiveness, but of course no one here would listen to it. ...

I'll listen - do you have a link?

[supdaf]

I drilled my bolts (hex) for safety wire. The aircraft mechanic in me likes it this way. I still use the schnoor washers but no problem with the wire.

[Deadeye]

I went with Stage8 bolts with locking clips and snap rings. Pain in the axx to install the tiny snap rings, but cannot come off.

[Gunter]

Good stuff.

I think the most important thing is to go underneath couple times a year and make sure the CV's are tight.

Gaskets will affect torque values and contribute to the bolts coming loose over time, IMHO.

I don't use gaskets, moon plates or LocTite, but I use lock washers and re-torque occasionally.

[Won]

Originally Posted by RWebb

I'll listen - do you have a link?

http://www.schnorr.de/uploads/media/informationsschrift_de_en_01.pdf

See Fig. 13. I see now the test surface was only 380 HV30 though.

This is from way back:

Reconstructing Constant Velocity (CV) Joints

Originally Posted by Jim Sims

Based on the limited amount of data I have available (I have a summation of the Schnorr loosening tests) this is my "take on it": The VS series are only significantly helpful if they improve and maintain the mechanical locking effect of the "bite of the serrations" into the contact surfaces. That is the main purpose of the "spring action of the Belleville shape"; the spring force generated is a small fraction of the tensile load of a tightened screw and doesn't significantly add to the clamping force generated on the CV joint flanges (which in combination with the friction generates a traction to carry the torque). The VS series is useful when used against hardened surfaces or limited area surfaces (slots or oversized holes) or with hardened bolts. On softer contact surfaces there is no point as the serrations of the S series are already embedded far enough (check out the some used "moon plate" washers). On the surface it would appear that the higher strength bolts should use the VS washers. The highest bolt strength class mentioned in my Schnorr test literature is also 10.9 ( and is associated with VS washers) which I believe achieves a significant portion of it's strength due to higher carbon content and hardening. I recall that the 12.9 strength class had an alloy content that may allow it to achieve it's strength without being as hard. Hence a VS thickness washer may not be helpful. I'll have to look up the head hardness of 12.9 versus 10.9 socket head cap screws. I do note that with the 8.8 strength class screws Schnorr appears to conclude the Schnorr serrated washers can be reused which is not the case with the 12.9 screws. Cheers, Jim

Additional information. Metric socket cap screw Rockwell thread hardness: 8.8 is C23-C34; 10.9 is C33-C39 and 12.9 is C38-C44 compared to C39-C45 for Schnorr serrated lock washers. So the Schnorr lock washers are of comparable or higher hardness than the 10.9 or 12.9 screws. However further consideration of the situation in a 911 CV joint still points to little or no gain in using a VS washer as it will merely embed itself more deeply in the softer steel of the moon plate or cv joint flange instead of applying more force to "dig deeper" into the hardened head of the screw on the other side. Think of the the Schnorr washer bearing against a "bed of putty" (the soft steel of the moon plate); it can only push back against the hard head of the bolt with the load the "putty" can support.

Enuf.

So perhaps that paper doesn't prove anything after all for 12.9 bolts. Draw your own conclusion!

[RWebb]

I found this here also

http://schnorr.com/docs/Handbook.pdf

but doesn't Fig. 13 relate to the Fatigue Life of a Disc Spring (like Fig. 11)?

I thought the concern was not about fatigue failure, but about the ability of the serrated edges of the Schnorr washer to bite into the materials (?)

my bottomline on it, is the washers are cheap, and I don't pull the CVs out very often, so...

[Won]

Yes it is a cyclic test chart but I didn't see it as a typical fatigue test, compare it to this and I think it makes more sense:



... puts this in context:



I agree 100% that they're cheap, disposable and should be replaced when possible. But at the same time if you don't have new ones handy it's not necessarily a panic inducing situation like so many here make it out to be.

[RWebb]

yup - I would definitely reuse them if I had no new ones at hand (and have done so)

might keep track of which ones were old tho - as per their claim of reuse "two or even more times"