Rear axle dust bellows change

[49willard]

As part of my drive train refresh, I am in the process of replacing the 4 bellows on the 1/2 shafts, 1 was torn. I initially purchased bellows kits by GKN. After some reading I decided to get at least the bellows themselves as Porsche original. I ordered just 4 bellows thru my local Porsche dealer. It appears that there may be 2 different types of bellows, those with a flange and those without the flange. Are they supposed to be interchangeable? The large diameter end is significantly smaller on the new (non flange/#90133229312) that I got than on the original bellows off my 1986 Cab.

[KTL]

The bellows for your later style axle service kits do not include a flange. So you want to be sure your flanges are in good shape. Often times people can let the axle dangle down from the transmission after it has been unbolted from the trans. That dangling will bend the opening of the flange.

The two different style of bellows are not interchangeable. If you look at the parts diagrams, you'll see the bellows have two different part numbers in two separate axle assembly pictures.

In the complete boot kit for your later axles, you get a boot, grease (throw this economy grease away and use good high quality synthetic extreme pressure CV grease), retaining straps and a metal end cap. When you do all four, you end up with two extra caps because the outboard CV joint at the suspension arm side of the axle does not have a cap. The outer CV joint has the stub axle welded onto the CV housing and therefore we can't install a cap there.

I would suggest that as long as you're diving into this, you'll want to take a look at the CV joint races/grooves. The inboard CV is easier to get a look at the grooves. The outboard CV is hard because of course it's tucked into the trailing arm and it's also not easily removable from the axle itself. Plus the outer bellows flange is crimped and o-ring sealed to the CV housing. The typical failure mode is the grooves tend to get pitted from the high loading they're under and lack of lubrication. The grease may be present but it breaks down over time and the insufficient lubrication allows for direct contact between the ball and race, creating a lot of wear.

[pkabush]

Originally Posted by KTL

The bellows for your later style axle service kits do not include a flange. So you want to be sure your flanges are in good shape. Often times people can let the axle dangle down from the transmission after it has been unbolted from the trans. That dangling will bend the opening of the flange.

The two different style of bellows are not interchangeable. If you look at the parts diagrams, you'll see the bellows have two different part numbers in two separate axle assembly pictures.

In the complete boot kit for your later axles, you get a boot, grease (throw this economy grease away and use good high quality synthetic extreme pressure CV grease), retaining straps and a metal end cap. When you do all four, you end up with two extra caps because the outboard CV joint at the suspension arm side of the axle does not have a cap. The outer CV joint has the stub axle welded onto the CV housing and therefore we can't install a cap there.

I would suggest that as long as you're diving into this, you'll want to take a look at the CV joint races/grooves. The inboard CV is easier to get a look at the grooves. The outboard CV is hard because of course it's tucked into the trailing arm and it's also not easily removable from the axle itself. Plus the outer bellows flange is crimped and o-ring sealed to the CV housing. The typical failure mode is the grooves tend to get pitted from the high loading they're under and lack of lubrication. The grease may be present but it breaks down over time and the insufficient lubrication allows for direct contact between the ball and race, creating a lot of wear.

Yep. Guilty as charged. I had my axles wired up but after rolling my car around many times the bailing wire came loose (my fault) and I distorted all of my flanges. I spent several hours getting them back into shape. Also, after cleaning and inspecting my CV joints I discovered they were all in need of replacement.

[49willard]

Kevin,
Thanks for your response, very helpful. I made the mistake of ordering the bellows which are specified for the 930 which must be different and has no flange. I have another set ordered, has to come from the west coast.