Quick cv Bolt question

[Brian in VA]

Hey, want to clean or replace my cv's, the psngr side is clunking. Anyway, the left has hex bolts but the right has something else. After looking here I mistakenly thought 8mm 12pt, but that isn't it. Maybe 6mm.....thought I'd look for suggestions before wasting more time/money on another driver. Thanks

[Targa Me]

How about a photo....

[LJ851]

They should be allen bolts. Your 1980 should have 8x1.25 bolts which use a 6mm allen driver.

[RWebb]

may be triple square

[Grady Clay]

There is a (long) thread worth studying in it’s entirely:
Reconstructing Constant Velocity (CV) Joints

Best,
Grady

[tshebib]

I had a mismatch of 6mm allen bolts and 8mm triple square bolts on my '80SC. Over the years various repairs may have contributed to different bolts being used. To make it more confusing I replaced the whole axle assembly with this kit from our host a couple of years ago Pelican Parts - Product Information: 923-332-033-02-M60. The original style bolts will not fit through these holes. When I took the transmission out this winter I forgot about the mismatch and stripped 2 bolts trying to use an allen socket. I still had the old axle assembly tucked away (yes, I know I'm a pack rat) and tried to fit these bolts into the flange. The non-threaded part of the bolt was too thick. I talked to Glen from the sales department here and he sold me 944 CV bolts which were threaded the whole length of the bolt. These were 8mm 12pt. Bottom line is you really don't know what you have because you're working on a 32 year old car that more than likely doesn't have the original bolts or axle.

[Brian in VA]

Sorry the pic I took doesn't show it well, I'll get another. So I'm thinking it really must need a 6mm triple square driver then, that's the only thing that makes sense. Allen on the left as you said. Another PO change.
And thanks Grady, I've had that one bookmarked for a while. I'm sure I'll be coming back with more questions later anyway (seeing as I haven't gotten started yet and I'm already asking)

B

[Grady Clay]

tshebib,

I recommend that you replace all of your CV joint bolts with new, known quality, correct length, 6-point internal hex bolts.
You can replace them one-at-a-time so to not disturb the CV joint seating against the flange.

The correct strength grade is “12.9”. These are NOT hardware store bolts.
The bolt threads should protrude through the flange by 1-2 (1½ is ideal) threads.
Make sure your Allen socket tool is in perfect condition.
Make sure your torque wrench is calibrated.
Use new Schnorr safety washers. The raised center goes toward the bolt head.

Does your 911 have the ‘moon’ 2-hole washer plates? If so, use them.

Inspect the tin cover seating surface for the Schnorr washers. These should have a good, flat surface to grip if no ‘moon’ washers.

Do not grease the bolt threads.
Inspect the threaded holes in the flanges for debris or rust.
Clean threads with a wire brush, ‘brake clean’ and compressed air. (Position the hole being cleaned ‘down’ to protect the lip seal. I additionally use a piece of cardboard, cut to fit.)

Do not use 12-point bolts, they are difficult to reach the required torque and ‘strip’ more easily.
Do not use bolts that are threaded the full length, they are probably not the correct strength grade.
The correct bolts must have the “12.9” stamped in the head of the bolt. Do not accept a bolt with printed “12.9”.


To clear up any possible confusion:
There are two different bolt sizes used for two different size CV joints.
The 108 mm OD CV joint uses a M10 (10 x 1.5 mm thread) bolt with an 8 mm internal hex. This is a “10 mm” bolt. The M10 bolts should be torque to 63 ft-lbs.
The 100 mm OD CV joint uses a M8 (8 x 1.25 mm thread) bolt with a 6 mm internal hex. This is an “8 mm” bolt. The M8 bolts should be torque to 33 ft-lbs.
Never confuse the ‘wrench size’ with the ‘bolt size’.
Never confuse the torque specs, either a bolt will break or become loose.
Always re-torque the bolts after 100 miles or so. Check at periodic maintenance.

Best,
Grady