915 Wavetrac Shim Question

[GenX Porsche]

I have unraveled a big transmission project, I know that's par for the course with a 915 of unknown origin, when I went to install a Wevo gate kit. I was living the Schrodinger's cat paradox, but once it was open I found worn dog teeth and then a spun bearing. BTW there are great articles here and a youtube series that gave me the confidence I could accomplish this task.

While I was in there I decided to install a Wavetrac and I am having some difficulty getting the preload perfect. I know I am shooting for a range of 26-36 in/lbs and I tossed a 2.9mm shim in and got 50 in/lbs and then went to a 2.8mm and got 5 in/lbs. When taking it apart I only had large shims while I know I could have a combination of a stack of large and small. I know they don't make the large shims in .5mm increments but I can't seem to find a part number for the small shims. Does anyone have that part number and have any opinions on if this will get my pre-load where I need it to be?

I am also having another weird behavior where I can't seem to get the feeler gauge side cover measurement, the side cover always bottoms out regardless of the stack. Could it be that my side cover has flexed over time? Any opinions here?

So far I have only touched the side cover side and the speedo side has a 2.8mm shim in it. I know this brings my stack to ~5.7mm and the ideal is 6.25mm but my stock configuration was 2.8mm on speedo and 2.9mm on side cover. I was going to check gear teeth pattern once I get this preload sorted out.

I appreciate any help.

[kevingross]

The shims you want are the 996.332.266.xx parts, available from 1.50 to 3.10 for the most part in 0.05 mm increments. Plus the 950.332.268.00 0.25 mm shim. The 915 and 950 versions of the shims are generally available, but a) they are much more expensive, b) they have one or zero "bites" allowing your puller to grab the race rather than the shim; the 996 have two "bites", c) they come in 0.10 mm increments.

There are tolerances in the shim thickness, which is to say they are not perfect and the measurements may jump surprisingly depending on the shim you use.

The "feeler under the diff cover" method is rubbish, utterly unreliably. Use a turning torque measurement. Note that the spec for turning torque depends on whether you are using FAG versus SKF bearings.

Especially if you have a magnesium case, yes, your case and side cover may have "flexed" a lot over the years. I serviced a mag case some years ago that took over 2 mm add'l shimming to get it right.

The Wavetrac should come with a spacer to be used if you don't have a "tone wheel" electric speed sensor, that is to say, you have a mechanical speed sensor. The Wavetrac spacer compensates for the thickness of the tone wheel you don't have. Good luck,

[GenX Porsche]

I want to bring up that I had an error in my original post. I am looking for a .05mm shim so I can make a stack totaling 2.85mm.

Thanks for the response and confirming my hunch that the side case cover isn't always the best marker. I assume if I bought an aftermarket it might be more accurate.

Regarding the Wavetrac, I am using the "tone wheel" as is but that is good info.

I pride myself in being able to find many hard to find things on the internet but I am having a tough time tracking down these shims. I tried our host, Stoddard, and the closest I got was Auto Atlanta here, http://www.***********.com/porsche-parts/hardparts.php?dir=986-97-04&section=305-02&pn=99633226669#a. Unfortunately there is no way to make a 2.85mm stack with the shims they have available. I also couldnt find this part number anywhere 966.332.268.00. Do you have any tips on where I could order from?

Thanks,
David

[Matt Monson]

What’s the description of that part number at the end?

[GenX Porsche]

That link leads to the exploded diagram of "Porsche Boxster 986 G86.20 Differential Rear Axle".

[Matt Monson]

You listed a part number that doesn’t come up. I asked for a description so that I can find it another way.

[GenX Porsche]

I see what you are getting at... was hoping that title would get you there but the search engine is a little lacking.

I verified that if you search for this part number, 99633226669, you can then go to the View Full Diagram to get to that url.

[Matt Monson]

What is a 996.333.268.00? That part number doesn't exist?

I have all the factory diagrams on my desktop. I don't need a link (pelican blocks certain competitors, BTW). I just need to know what it is.

[GenX Porsche]

I have seen others post about large shims with the chamfer then smaller shims that stack on top. I think Kevin was trying to provide a part number for those smaller shims. Do you see something in your factory diagrams? The part number, 99633226669, is for a large shim. I am looking for a shim in the .025mm or .05mm range.

[Matt Monson]

950.332.268.00 is the .25mm shim It will be very hard to find.

The only way you will be 2.85 is with a 2.6mm and a .25mm. You will most likely have to go 2.8 or 2.9 and consider it good enough.

[gled49]

996 differential carrier shims range from 1.5mm (996 332 266 50) to 2.8mm (996 332 266 76) in .05mm increments. These fit everything but early ALU 901 differentials. 915 shims go up to 3.7 but availability is limited and cost a lot more, only available in .10mm and need .25mm shim to achieve .05 adjustment. Those shims are not recommended because they will spit out if carrier bearing start to spin. I will fuge my pre-load to get better adjustment. I will stack 996 shims to get what I need.

[Matt Monson]

Carrier bearings only spin when you reuse a bearing or on an old tired diff. New set up with new bearings has pretty much zero risk.

[kevingross]

Apologies for my typo, corrected in the original post but 0.25 mm is 950.332.268.00, 2.60 is 996.332.266.72. Both show as available from Porsche. Or if you ask someone who services a lot of Porsche transmissions, they might be nice enough to provide you a couple of good used ones or even shiny new ones.