CV Joint gaskets

[patkeefe]

Hi all.
I am putting the SC back together, and am wondering why the parts diagram shows only gaskets at the flange mating points, inner and outer. Why wouldn't there be a gasket on the mating surface between the bootie flange and the CV joint?

And, the joints in my SC have a chamfer on one side only, not on both. Why is that? Anyone know? I will search some more, but I think I am missing something here.

TIA,
Pat

[Gordo2]

Ran into the same thing when I refreshed the CV's on my 83. To compound the issue, some people recommend not using gaskets between the mating surfaces.

I can't recall for sure, because I was debating the options at the time, but think I went with how things were laid out in the parts manual breakdown - gaskets between each flange.

Good luck, Gordo

[patkeefe]

Thanks, Gordo

[Grady Clay]

Pat,

The CV joint-to-flange is metal-to-metal contact.
The gasket fits in the recess and prevents grease from getting between the metal surfaces.
You must be careful to not get any gasket between the metal contact surfaces.

The tin cover for the boot is a press-fit on the CV joint.
It seals very well.

This is the best thread:
Reconstructing Constant Velocity (CV) Joints
While long, it is worth the read and study.

Best,
Grady

[patkeefe]

Grady,
Thanks! I understand the gasket fits into the recess. However, the tin cover you speak of is not a press fit onto the CV joint. From my point of view, I see no difference in the mating on either side of the CV joint.

And, I have read Randy's thread before, but I will peruse it again.

[patkeefe]

Grady:
I suppose this is the tin cover you speak of? My SC is not like that. The boots are integrated into a flat steel cover, which are machined to take the gasket. I will get a photo of mine tomorrow.
Pat

[euro911sc]

Pat,

I just rebuilt my axles start to finish. I skipped the gasket. I also put a skim coat of red RTV across the joint of each CV to the Boot flange and the drive flange (trans and hub sides). I am not a proponent of RTV, but in this instance it works very well. I just put on enough to push into the chamfered edges where the CV's meet the other parts. Do this post torqueing and make sure the surfaces are dry and clean of CV grease. Just put your finger on the joint and spin the axle. When it comes time to remove them again just run a razor in the groove and they come apart. I have zero leaks now.

[patkeefe]

Thanks Michael:
Now Grady has me concerned (after reading the thread he linked) about the clamping forces and frictional components associated with the CV transmission of torque to the wheels. That would mean that the mating surfaces need to be really clean and grease free, which is almost impossible for me to do. I need to do some more analysis on the power transmission.

I did have gaskets in one of my axle shafts, I noticed. I suppose it was a comparative analysis science experiment I did a few years ago. That side did stay a lot cleaner.

[sc_rufctr]

Someone will probably shoot me for posting this but...

I removed my gaskets years ago and have never had an issue with grease coming out or anything.

[tobluforu]

Originally Posted by sc_rufctr

Someone will probably shoot me for posting this but...

I removed my gaskets years ago and have never had an issue with grease coming out or anything.

No, as I have read that many do this.

[Grady Clay]

SWB 911 & 912 never had gaskets.

Porsche installed the ‘outside’ (outside the bolt circle) gaskets starting with 1969 LWB 911 & 912.

About ’75, Porsche changed to the ‘inside’ (inside the bolt circle) gaskets.
These are softer gaskets had have one side with glue.

Search. There is a thread where I describe how to make locating pins to ease ‘no-grease-mess’ installation.

Best,
Grady

[RoninLB]

no gaskets here

no leaks either

[patkeefe]

As I said, I had one axle with gaskets on the boot flanges, and one axle without gaskets. On both axles, the CV joint to flange (either stub axle or transmission) had gaskets. My boots and the drive flanges are no different from each other (my boots have the flat mounting surface, looks like
Pelican part 923-332-037-00-M84). The boots have the same machined pattern in them to accept the gasket as the flanges do.

So, either the factory wanted to waste money on machining a part that did not need to be machined, or:
The factory assumed that the grease would not fly out (if this is the case, why bother with gaskets on either face of the CV?), or:
The gasket is shown only on the outside ends of the CV in order to increase the frictional component of the CV to flange mating surface (from the Jim Sims/Grady?Island discussion in the linked thread, where we deduced the bolts are not made to carry any shear load), or:
None of the above.

From this and other research I have realized we can run with or without gaskets. I prefer to use them on the outer mating surfaces of the CV. I am curious about the boot to CV interface. Inquiring minds want to know.

Pat

[patkeefe]

FWIW, I did notice that the gaskets are thicker than the space within which they should fit. So, the CV will stand off from the flange a bit, like maybe 1/2mm or so. Small yet substantial. if we believe the power transmission is mostly due to the frictional component of the joint-flange interface.

I trimmed mine flush with a razor blade.

[Grady Clay]

Originally Posted by patkeefe

FWIW, I did notice that the gaskets are thicker than the space within which they should fit. So, the CV will stand off from the flange a bit, like maybe 1/2mm or so. Small yet substantial. if we believe the power transmission is mostly due to the frictional component of the joint-flange interface.

I trimmed mine flush with a razor blade.

No, the gasket crushes to form the seal.
If the two surfaces are clean and free of pieces of interfering gasket, you get the desired metal-to-metal contact.

Best,
Grady

[Flat6pac]

but be sure to retorque after a short time or the 6mm bolts will work themselves loose.
Bruce

[Rodsrsr]

When I reinstalled my motor recently I used new CV bolts and gaskets. The gaskets that I purchased from our host now have an adhesive on one side, so all you need to do is clean the groove very very well and the gaskets will stay in the recessed area no problem. The time before this when I had the joints apart, I didn't install the gasket because the brand I used didn't have the adhesive side which makes it too hard to keep it in place. In my experience, without the gasket it's prone to leaking.

[patkeefe]

Let me explain this a little better. I put a gasket onto a wire brushed and acetone scrubee cleaned flange. I used the gasket with the adhesive as mentioned above. I installed a cleaned CV joint outer assembly (a CV with no inner cages or balls) onto this flange, and torqued the assembly, and left it on for a few days. The gasket DOES NOT CRUSH. I have thus concluded the gasket is a bit too thick for the application. However, I have noticed that the old gaskets I had on did seem to be crushed, so I am unsure of whether it was the effect of the grease, thermal effects or what that made them seem crushed. Maybe the gaskets I had on before were thinner.

I have this assembly sitting on an outer (wheel) flange at the moment. I will try and get a photo of this tonight, and measure the gasket thickness and space between the joint case and the flange.

[Grady Clay]

Pat,

WOW!
You are saying that even when torqued, the gasket prevented metal-to-metal contact?
Are you able to fit a feeler gauge in the space where there should be contact?
How much? ~0.50 MM?
Where did these gaskets come from?

Best,
Grady

[patkeefe]

Grady, I am going to scrutinize this other joint that I have assembled tonight, and see what kind of gap is in there. I still have two of these new gaskets, untouched, and will put a micrometer on them. The gaskets came from a reputable Porsche shop, not our hosts.
A picture is worth a thousand words.