CV Bolts sourcing for '74 911 and CV question

Tom '74 911 · 07:51 AM

Hi -
First off, I have done a lot of reading up including the oft mentioned Constant Velocity (CV) Replacement Thread - a great one w/almost too much info.

I just want to have some verification. I have a '74 911 w/the 4-bolt CV flanges. I took one bolt out last night to verify what the current set-up is and it's 10x48mm - just as PET and Pelican indicates. There are also backing (moon) plates and lock (schnorr) washers. I know I can reuse the bolts if they're in good condition, but I wanted to have some spares on hand + new washers etc...

I've looked at McMaster Carr and the bolts only seem to come in 5mm lengths - so I could get 45mm or 50mm. Pelican sells the correct 48mm bolts for $7.25 ea. - and they look to have a 12 point hex head - mine currently have a 6 point (8mm) allen head.

So my question is where can I get the correct 10x48mm bolt w/a 6 point head? I'd love an option that is more affordable than $7.25 ea., but it is what it is.

Any help is greatly appreciated!

Thanks,
Tom

edit for add'l question:

Also, I wanted to ask about grease in the bolt holes. I seem to remember reading that the CV bolts are supposed to be installed dry. Is that correct? I ask because when I pulled out one last night, it was covered in stinky grease - is that a sign that the joint needs to be rebuilt?

Zef · Zef's Garage

www.boltdepot.com

Tom '74 911 · 02-15-2007, 08:12 AM

zefsuper911 -

Thanks for the link. They only seem to come in 5mm increments - same as McMaster Carr see this page from the site.

Did I miss something?

Thanks,
Tom

Tut · 02-15-2007, 08:15 AM

Buy the 50mm length and then take them to a machine chop to me shortened. Maybe a buck a bolt to do it.

IROC · IROC's Garage

I'm not intimately familiar with '74 CV joints - is there any reason why an extra 2mm (.080 inches) of length would hurt? If not, the 50mm long screws would be fine (I've never seen these things in anything other than 5mm length increments). I think most metric socket head cap screws are 12.9 strength, but that's what you want to look for.

I replaced my CV joint screws with some locally available ones. There's nothing magical about them.

Tom '74 911 · 02-15-2007, 08:21 AM

Quote:

Originally posted by Tut
Buy the 50mm length and then take them to a machine chop to me shortened. Maybe a buck a bolt to do it.

Tut -
I did read about that possibility as well. My problem is that I live in a small mountain town, nowhere near such services - sometimes a curse, more often a blessing! Maybe I will do some calling around though.

Also - I read in a thread a while back that you bought a bunch of the lock washers in bulk. Any chance you need to rid yourself of a bunch of them still?

Thanks,
Tom

Tom '74 911 · 02-15-2007, 08:27 AM

Quote:

Originally posted by IROC
I'm not intimately familiar with '74 CV joints - is there any reason why an extra 2mm (.080 inches) of length would hurt? If not, the 50mm long screws would be fine (I've never seen these things in anything other than 5mm length increments). I think most metric socket head cap screws are 12.9 strength, but that's what you want to look for.

I replaced my CV joint screws with some locally available ones. There's nothing magical about them.

According to others, there is an optimum extension of the bolt past the flange - something like a thread or two - I can't remember exactly. It's all in the "Constant Velocity (CV) Replacement Thread" I linked to in my first post. The bottom line is: it may matter, but I'm not certain and can't prove it from my own direct experience.

Tom

island911 · 02-15-2007, 08:31 AM

Quote:

Originally posted by Tom '74 911
.. .
Also, I wanted to ask about grease in the bolt holes. I seem to remember reading that the CV bolts are supposed to be installed dry. Is that correct? I ask because when I pulled out one last night, it was covered in stinky grease - is that a sign that the joint needs to be rebuilt?

Because your CV's have pins, you needn't worry so much about uber clean mating surfaces. . . .or moon-plates . . or Schnorr washers.

That is, those pins are there to take the shear load between the flange and CV . . . a shear load that is compromised on 6-bolt CV with grease on the mating surfaces. ...which inturn can shimmy bolts loose.

Tut · 02-15-2007, 08:31 AM

IROC,

When I did my CV boots 55mm was fine on one side, but a little too close to the trans. for comfort on the other, so I had them cut down. So 2mm can make a difference.

Tom,

How many do you need? I ask for the cost per washer plus postage. It ain't much.

I live in a very rural area also. Maybe you could contact a machine shop by phone then ship them to the shop.

Tom '74 911 · 02-15-2007, 08:58 AM

Quote:

Originally posted by Tut
IROC,

When I did my CV boots 55mm was fine on one side, but a little too close to the trans. for comfort on the other, so I had them cut down. So 2mm can make a difference.

Tom,

How many do you need? I ask for the cost per washer plus postage. It ain't much.

I live in a very rural area also. Maybe you could contact a machine shop by phone then ship them to the shop.

Thanks Tut. I will send you a PM re:the washers.

Tom

911pcars · 02-15-2007, 10:08 AM

2mm can be easily taken up by a hardened 2mm spacer/washer under the bolt head. Let's not obsess too much.

Sherwood

Early_S_Man · 10:19 AM

M10 x 50 Allen bolts, DIN 12.9 property class bolts work fine on '72 - '75 CVs without modification ... but, if you want to save 32 gms or so, have at the grinding wheel???

http://www.metricmcc.com/catalog/Ch1/1-37.pdf

Porsche_monkey · 02-15-2007, 11:03 AM

Quote:

Originally posted by Tom '74 911
Tut -
My problem is that I live in a small mountain town, nowhere near such services -

Tom

So small they don't have grinders or hack saws?

ros74911 · ros74911's Garage

hey, tom. i usually go to this site if i'm stuck on something. here it is.
http://www.***************/productpage.aspx?pid=101811&name=CV+Joint+Bolts

Tom '74 911 · 02-15-2007, 11:28 AM

Quote:

Originally posted by 911pcars
Let's not obsess too much.

Sherwood

Perhaps this sums it up perfectly. I try not to obsess too much - I really don't have the time! But, I also want things to be right. I do hate to go through the process of ordering parts and then find out that they're not the right ones or don't fit etc... I think that Constant Velocity (CV) Replacement thread is a mixed blessing. The discussion there DID make much adu about 2mm and how one SHOULDN'T just hacksaw or grind off 2mm from a 50mm bolt as the resulting thread entry and taper would not be right - or something like that.

If the 50mm bolts will work for me, as Warren suggests, than that's GREAT! If I can take my grinder and grind off 2mm if I need to, and it's all good at the end of the day, even better. I just don't want to make any MAJOR mistakes or create any unsafe situations - if I can help it.

Thanks for the responses so far!

Tom

Porsche_monkey · 02-15-2007, 11:32 AM

What do you think the machine shop will do? Set it up in a lathe and re-cut the thread? No, they will put a nut on the bolt, hack or zip-cut it, and file the end.

The trick to fixing the threads is to a) put a nut on the bolt (below the cut-off point) b) use a file and round the end slightly, filing almost perpendicular to the bolt c) remove the nut, and that will clean up the thread for you.

No obsessing required.