What bolts for a 4 bolt flange CV joint? ('74 915 transmission)

[Hotwatermusic]

I want to get new bolts for my CV joints, as I am about to mount them back to the transmission. Problem is I can't seem to find the correct size to buy here on Pelican. Can anyone direct me to the proper bolts for a 4-bolt CV joint flange on a '74 915 transmission? I tried to measure my current bolts but their size didn't seem to match anything available for sale. Thanks!

[bullethole]

Do you have the moon plates between the bolt and the flange.. You also do not indicate if these are 100 or 108mm. they use a different diameter bolt (8mm vs 10mm if i remember correctly). If they are without moon plates it should be a 50mm length bolt.

search flanges in the forum.. tons of great info on all this

[JeremyD]

I have a set of stage 8 for my 1974 - I'll sell for 1/2 price if you want

[T77911S]

go to fastenal. you can get a bag of 50 bolts and the washers for what a set for the car will cost.
they come in 5mm lengths so make sure you get ones that have 2-3 threads showing on the flange side.

[RWebb]

are you sure your current bolts are correct?

you can also download the PET for the p/n and other hardware, or call Pelican by phone for help

be SURE you review the proper installation procedures - it is not uncommon for people to mess these up and then have a loose axle flailing around tearing up some expensive parts

[Hotwatermusic]

Originally Posted by bullethole

Do you have the moon plates between the bolt and the flange.. You also do not indicate if these are 100 or 108mm. they use a different diameter bolt (8mm vs 10mm if i remember correctly). If they are without moon plates it should be a 50mm length bolt.

search flanges in the forum.. tons of great info on all this

Yes, there are moon plates between bolt and flange. I am at work right now so I can't go out and measure again, otherwise I'd tell you the exact length the bolts are. I just know their size didn't match any length that Pelican had for sale.

[Hotwatermusic]

Originally Posted by T77911S

go to fastenal. you can get a bag of 50 bolts and the washers for what a set for the car will cost.
they come in 5mm lengths so make sure you get ones that have 2-3 threads showing on the flange side.

I would love to do that, but have no idea what I would need to get or how to cross-reference it exactly. Is there an exact match on Fastenal I should be looking for? What grade/alloy does it need to be to handle CV joint conditions?

[Hotwatermusic]

Here are the measurement for the bolts:









Are they officially 8x50's?

[Grady Clay]

WRONG WAY TO MEASURE




The bolt length measurement is under the bolt head to end (green arrow).
The diameter is at the threads or shank (violet arrow).

Spec is to have the threads protrude through the flange 1-2 turns with 1.5 turn ideal.
The limiting factor is to have sufficient clearance to the transmission casting as the flange ‘floats’ axially.
In this range of lengths, commercial bolts are usually available in 5 mm increments.
Non-5 mm increments (48 mm, 53 mm) are available from Porsche (for a price) with a Porsche part number.
You can have a machine shop shorten these bolts so long as the ‘lead-in’ thread is provided (simple sawing them off doesn’t work well ).

911 CV joint bolts are either M8 (8 mm x 1.25 mm/thread) or M10 (10 mm x 1.5 mm/thread).
While I have seen some 12-piont (XZN) socket head cap screws used, the best is the regular 6-point internal hex ‘Allen’ head.
The 6-point is least susceptible to ‘rounding-out’ the wrenching feature.
The M8 bolts use a 6 mm Allen and the M10 bolts use an 8 mm Allen.
Be sure to use a new or freshly 'dressed' tool.

These bolts are not ‘hardware store’ stuff.
You MUST use ISO strength class 12.9 (old DIN 12K) socket-head cap screws.

You should use new Schnorr safety washers every time.
Note the orientation in the image above.

The purpose of the hardened ‘moon-plate’ 2-hole washer is to provide an intermediate hardness material (between the very hard Schnorr washer teeth and soft mild steel tin boot cover) for proper safety washer grip.
If in doubt (or Porsche’s ‘bean counters’ omitted them), you can install ‘moon plates’ so long as you have proper length bolts.
The ‘moon plates’ have come in a number of shapes in order to clear the shapes of the tin boot covers.
Make sure the ‘moon plates’ clear properly.

This is one of the best threads on this subject:
Reconstructing Constant Velocity (CV) Joints
While long, it is worth studying end-to-end.

Be sure to use a calibrated torque wrench.
The ‘general consensus’ is the M8 bolts are torqued to 33 ft-lbs and the M10 to 63-65 ft-lbs.
Be sure to re-torque after a few hundred miles of driving.

Best,
Grady

[RWebb]

outstanding, Grady!

[bullethole]

you should be able to get the bolts through McMasterCar