Which parts need to be changed when stock LSD is worn out?

[AlexJ]

Which parts have to be changed when LSD is worn out?

Considering that the LSD is all complete and solid, just not working (a few lbs. under the limit factory spec), I think it is only necessary to change the parts indicated as inner disc (part numbber 928 332 551 00), which look to me as the only parts that really wears.

Am I right or any other parts should be changed?

Appreciate any help.

By the way, what is the meaning of 3 different sizes of the disc with external splines (part numb 917 332 552 10)? Is that to compensate the inner disc's wear?

[Bill Verburg]

Originally Posted by AlexJ

Which parts have to be changed when LSD is worn out?

Considering that the LSD is all complete and solid, just not working (a few lbs. under the limit factory spec), I think it is only necessary to change the parts indicated as inner disc (part numbber 928 332 551 00), which look to me as the only parts that really wears.

Am I right or any other parts should be changed?

Appreciate any help.

By the way, what is the meaning of 3 different sizes of the disc with external splines (part numb 917 332 552 10)? Is that to compensate the inner disc's wear?

inner disc are the friction plate discs the outer are the plain steel, both are subject to wear as is the belleville washer at the end of the stack
here's what's inside


stacked in order


the empty case which the stack goes into


I'd rebuild w/ Guard Transmission plates

[AlexJ]

Thanks Bill.

Do you know why there are different measures for the plain steel discs?

[cdrik915]

Ask for carbon dics.

Available at Porsche.

Definitive .

[AlexJ]

Do you know the part number?
Is it more expensive comparing with the normal ones?

[Bill Verburg]

Originally Posted by AlexJ

Thanks Bill.

Do you know why there are different measures for the plain steel discs?

Part of tuning a LSD is stack height which contributes w/ belleville selection to stack preload.

More preload increases the effectiveness of the LSD at all times because the normal force on the clutch discs is increased at all times, sometimes to too much. Modern practice is to use lower preloads so that the LSD isn't intrusive until you want it to be so. This is possible because of the ramps seen on the stub-axle protuding from the pinion-wheel, the ramps work as wedge forcing the two shells to move slightly apart and lock the differential in accordance with the number of clutch plates used, but only when power is applied either by the engine or the brakes. The 993 LSD shown in my first post is a 25/65, the steep ramp is the acceleration ramp, the gentler ramp is the brake or deceleration ramp, the gentler ramp allows the end shells to be forced further apart applying more limiting differential action under braking.

The rule of thumb is: the more the diff limits slippage, the more the car will tend to go straight or understeer - up to a point. On the power side, if enough torque is applied to spin both wheels, the car will snap into oversteer. This last is the reason manufacturers are loath to have LSD's as standard on their more mundane vehicles

[cdrik915]

Originally Posted by AlexJ

Do you know the part number?
Is it more expensive comparing with the normal ones?

No , but i 'm going to try re-finding it.

I remember the price was'nt expensive.

[AlexJ]

Thanks Bill for the explanation.

cdrik915, would be great if you manage to find that information. Thank you!