Limited Slip Diagram/Info ?

[350HP930]

Does anyone have an exploded drawing of a 930 limited slip mechanism they can post?

I am suprised my factory manual has no information on the limited slip setup.

I am also curious as to if the coupling factor can be adjusted.

Thanks.

[Eric Coffey]

AFAIK the 930 units look similar to the 915 units, and are built the same. You can stack the clutch plates to get you anywhere from 40-80% lock-up. It comes set @ 40% from the factory, just like the 915's.

[Porschekid962]

I have one on the computer at work! its an aamco program but the pics are from pmna i think. I will print one out tomorrow and try to get it scanned and in the computer at home and posted soon. No internet at work so I cant lurk on the boards, booo. Cheers.

[Grady Clay]

Here is the 930 diagram:
"
"
(C) Dr. Ing. h.c. F. Porsche A.G.

I'll add some content when I get finished interviewing surgons.

Best,
Grady

[350HP930]

Thanks Grady.

Now I'm wondering if I should leave it at 40% or if I should bump it to handle the extra power I will need to deal with.

Has anyone here tweaked theirs?

If the above diagram is 100% correct it looks like all that might be required to adjust the unit is moving a couple of the disks around.

[Eric Coffey]

Originally posted by 350HP930
Now I'm wondering if I should leave it at 40% or if I should bump it to handle the extra power I will need to deal with.

Just stack it to 80% sissy.

[350HP930]

I think that would aggravate my understeering on tight courses a little.

[Grady Clay]

For track use, I like it on the very tight side. That means the order is: 3, 4, 6, 5, 6, 5, 8. #5 and #7 are the same part. This order is from outboard L & R in to the differential in the center. There are different disc thickness available – 1.9, 2.0, and 2.1 mm. You will need to buy two #6 discs in addition to replacing worn discs. Always save your old discs for future adjustment. The torque spec (one axle flange to the other) is 29 – 58 Ft-Lbs. You want it at the high end, perhaps as much as 70 Ft-Lbs.

The disadvantage on the street is the LSD clutches tend to be grabby and the rear tires chirp when going around a sharp turn. It will also increase the rear tire wear.

For street only use, leave it at 40%. Make sure all the parts are like new. Of particular importance are the little “notches” in the two #8 parts. Those ramps, in conjunction with the two #12, are what apply the increased clamping force on the LSD clutches with increased torque through the differential.

Always reassemble with new ring gear bolts and locking plates.

FWIW, the outer spline discs have a 917 part number.

Best,
Grady

[350HP930]

Thanks a ton Grady, thats just the kind of info I was hoping for.

I am rather suprised that you are suggesting new ring gear bolts though. The originals are some very high grade bolts with no signs of sheer damage.

Why do you suggest replacing them?

[Grady Clay]

There are a few fasteners in a drive train that I consider use-once type. This is not because they are damaged or wear out but because of the devastation should they fail. This is particularly true of a 930. The fasteners are; rod nuts and bolts, flywheel bolts, ring gear bolts, and axle bolts. For some extreme uses I had new fasteners X-rayed in two planes and magnifluxed.

Take the ring gear bolts and axle bolts. A 3.3 Turbo puts out about 300 Ft-Lbs torque at 4000 RPM. Shifting into second where you are at the max torque multiplies that by 1.3. Then the ring and pinion multiply that by 4.2. The result is 1652 Ft-Lbs torque applied via the ring gear bolts and the axle bolts. If the revs aren’t matched that figure can increase from inertial loads. There can be huge shock loads if the tires loose grip and suddenly regain grip.

If you warm the engine up and improve the tire grip it makes for still more loading.

The bolts actually provide a clamping force on the parts under them. Maintaining that clamping force is critical. If that force is compromised, things get progressively worse in a hurry. These are VERY expensive automobile parts. Think of the cost of Space Shuttle hardware and the result if some critical bolt fails.

The analogy is the horseshoe nail that failed … the battle was lost.

I look at new hardware in these locations as cheap insurance.

Best,
Grady

[350HP930]

Well, since I am a cheap bastard I will just magnaflux mine instead.