Sombrero56

Hello,
I need change roller bearing of my differential (987-1 of 2005).
I would change also shim but I don't know which is the good ?
Into katalog I read several reference with different size. What's good ref ? I need unmount and after buy ?

KevinGross

The shims need to be selected to re-establish 1) carrier bearing preload, and 2) ring-to-pinion free play (also called backlash). I don't have the specifications handy, but if you are serious about doing this yourself and investing in the tools needed, let me know, I can look it up.

Sombrero56

Hi KevinGross,
I'm interesting by all information of this works.

KevinGross

For the Boxster five-speed transmission, turning torque for the differential with new bearings should be in the range of 2.5 to 3.5 Nm. A picture from the workshop manual procedure for this, showing the factory's recommended tools:

The turning torque gauge can be any commercially available one that has a range of, say, 1 to 5 Nm. I use the one originally called for in Porsche manuals, which is expensive and may no longer be available. It was made by OTC and distributed through the VW/Audi tools program as US1064. But you could use, for example, Snap-on's TESI10L.

The backlash or free play should be in the range 0.12 to 0.22 mm. Here's a picture showing its measurement with factory tools.

Measurement is specified by Porsche at the outer diameter of the ring gear teeth (rather than the ring gear mounting base - small difference). Note that the 72 mm is in effect added to 16 mm for the VW521/4 tool, which is 32 mm across-the-flats, and so the net radius from centerline is 88 mm for the Boxster five-speed. You can improvise your own tooling, but it's made a little more difficult for transmissions that don't use a center bolt on the output flange because you need to find a way to lock the tool to the differential's spigot.

I hope this is helpful.

Sombrero56

Thank you Kevin for all.

Sombrero56

Hi,
today I changed the 2 bearing of the differential, no problem.
I have checked the 2 flanged shaft bearing and think they are worn.
Into manual is writing :
39 09 19 REMOVING AND INSTALLING DIFFERENTIAL
"The flanged shafts are installed with polygonal bearings. The rough running of these bearings when the flanged shafts are not installed does not indicate that the bearings are faulty. The polygonal bearings can be replaced only with the flanged shaft."
How as sure that ok or not ?

KevinGross

The polygonal bearings aren't serviceable, and they are kind of a weird thing that I don't fully understand. I am not aware of any history of frequent failures of them. So, unless you are seeing problems with the transmission, shafts, etc once installed, I would just leave them alone.

You can read this article to learn more about them: https://www.schaeffler.com/remotemed...pi11_de_us.pdf

Sombrero56

I read this article when I search information of bearing poligonal.
At begin i would change bearing of differential because i have a noise only when I accelerate (after drive trackday).
Finally bearing aren't destroyed. I changed them by prevention.
Then i think bearing poligonal.
I mount all and check on the road.

Sombrero56

Hello,
For information, I changed bearing last week but only these tapered roller bearings. The bearing poligonal didn't can change, it's kit of Flanged shaft.
The shim is use for adjust the torque of differential when all is close. For sample, i need use small shim to right and big shim to left for have backlash.
Thank for your help, see you bye.