CV joints: how much grease? Thin flange boots?

[Brian Cameron]

A couple of questions on CV servicing:

Replacing all 4 CV boots and 2 of the joints (the other 2 were replaced just a handful of miles ago). Getting ready to repack with molybdeum disulphide grease.

1 How much grease should i pack into the joints?

2 And should extra grease go into the boot also? I don’t imagine i should completely stuff the boot with grease... or should I? How much grease is the goldilocks amount?


The new GKN Loebro boots are thin flange vs the oem originals which had thick flanges. Consequently when I did a test fit I discovered that the 50mm outer CV bolts now bottom out and jam the hub so it won’t turn. Inners are ok, a couple of threads show through the output flange, but don’t contact anything.

3 Do i need to use moon spacers, and if so, are these needed on all 4 cv’s? Is this just because of the flimsy thinner boot flanges?

4 Again, if the moon washers are needed, are these the ones noted for sportomatic, ie 911-332-191-00? Or is a different size / part number needed?

5 i was planning to cut the outer bolts to 47mm length on the outers, to prevent the jamming: is this a good idea, or should i get shorter bolts instead? Tried to find part # for 45mm bolts bit not sure if there is such a thing since I’m not having any luck...

Ok, 5 questions is more than a couple, but thanks in advance for any sage advice from the forum!

[midnight911]

move the spacer kinda thing in the flange to the GKN flange. That way you don't have to worry about the bolt length. Now, I do suggest you look for moon plates and schnoor washers and use longer bolts to accommodate those materials.

I use very cheap EMPI moon plates for VWs p/n 875081. Fraction of price of a Porsche part. Schnoor washers and longer bolts were sourced from McMaster Carr.

When you buy GKN boot kit, they send you a small bag of grease for one CV. Not sure how much but perhaps you can get the amount from someone.

[SCadaddle]

I seem to remember from a few years ago while servicing the joints on my SC the spec on the amount of grease per joint was 5 oz. and no, I did not add any extra to the inside of the boot.

[manbridge 74]

Leave some air space. No need to Uber pack them.

[OldSpool87]

Read the epic CV thread and bask in the wisdom of Grady and others:

http://forums.pelicanparts.com/porsche-911-technical-forum/222537-reconstructing-constant-velocity-cv-joints.html

The moon plates can be sourced from JBugs if not found here at our host. Belmetric for longer bolts and Schor washers to lock it all up. It’s a great project. MESSY.

[Alex66]

Re 1) As per Porsches Workshop Manual it's 80 g which is about 3 oz. per joint

[safe]

Not too much grease, I pack the cv pretty good, but not much, if any, in the boot.

[OldSpool87]

Plug the bolt holes with paper towel and chill the grease overnight in the fridge. It makes for easier packing and clean up upon assembly to flanges.

[KTL]

I saw this old Buick instructional video last week and it shared some interesting info.

https://www.youtube.com/watch?v=SqhjGs2zFLo

-The predetermined amount of grease is said to be 1/2 for the joint and 1/2 for the boot. I have always thought it's silly to put grease in the boot because doing so doesn't serve any lubrication purpose. Maybe the intent is to use that extra grease as a "dam" to minimize grease migration from the joint when the grease warms up during operation? I have always just put a heavy dose of grease in the joint to make sure it's well lubed throughout, plus a little bit extra for good measure, and left the boot dry.

-The line around the joint housing is a measuring point. You use that line to measure from the small end of the boot to the line to set the amount of boot compression. It's basically like setting the "air pressure" in the boot.

Here's the part where he demonstrates the measuring https://youtu.be/SqhjGs2zFLo?t=1186

All told it's a pretty cool video from back in the 90s that gives a lot of basic but educational technical information on joint types (ours is a cross-groove type), boot types and some service/installation procedures.

[Stimorolgum]

My CV joints boots are starting to crack. The car has 200.000 km or 140.000 miles.
How long do these joints last? Maybe better to replace the whole unit.

The car has no track racing history, mostly regular driving.


Cheers /M

[KTL]

The old joints are pretty durable. I have seen some 20+ year old joints that still look good and can be re-greased along with new boots. But I suspect when you take them apart, you'll may find a pit in grooves where the ball bearings ride. The pitting occurs because the grease degrades with time and you end up with metal-to-metal contact.

Typically the most economical thing to do is buy a complete remanufactured axle(s). When you buy individual joints and boots, the collective cost is usually the same or more than a complete remanufactured axle.

[Stimorolgum]

Originally Posted by KTL

The old joints are pretty durable. I have seen some 20+ year old joints that still look good and can be re-greased along with new boots. But I suspect when you take them apart, you'll may find a pit in grooves where the ball bearings ride. The pitting occurs because the grease degrades with time and you end up with metal-to-metal contact.

Typically the most economical thing to do is buy a complete remanufactured axle(s). When you buy individual joints and boots, the collective cost is usually the same or more than a complete remanufactured axle.

You are probably right. My 911 is from 1973, so a long time for that grease to degrade.
And I do prefer to buy the complete axle, so much easier.

[old man neri]

Originally Posted by Stimorolgum

And I do prefer to buy the complete axle, so much easier.

Mine have 300 000km. I have replaced the boots and grease a few times in the last 10 years of owner ship. My only concern with your statement is that I am not confident that replacement parts are not the same quality as the originals.

[Kraftwerk]

Yeah nothing wrong w/ the axle.. just the joints need replacing... Each new CV comes with an 80g. bag of grease, so I suppose that's an answer, of sorts.

[Ian Comerford]

When I last rebuilt mine I was advised to use synthetic CV grease as it did not migrate when warm/hot.

Ian

[safe]

Originally Posted by Kraftwerk

Y Each new CV comes with an 80g. bag of grease, so I suppose that's an answer, of sorts.

Thats way too much...
Plenty of grease in the cv and some in the boot. Using to much will just heat it up and push it out the small end.

I learned from someone (cant remember who) that had problem with CV life when racing that less grease made the CVs last longer. It didn't heat up the grease to the same extent.

I've always kept the "grease level" sparse in my CVs. Grease have never pushed out anywhere, I have no ties/clamps on the small end either.

I changed my CVs when I bought my car (1977 targa) at 100.000 miles, now at 150.000 miles they still look good. Still using the original thick flange boots, lasts forever...

[KTL]

Quality of grease plays a big part. Economy grease turns into thick oil over time and doesn't stay in the joint as well as a quality synthetic.

I agree with Magnus on the old thick flange boots. Those old boots are made of thick long lasting rubber. The newer boots are a thinner section of rubber and not nearly as durable.