I've seen this thread here about the optional rear LSD in Turbo.
I have it in my 2007 997T, no 40k miles.

My question is - is this "fit and forget" item or does it wear out with time and has to be replaced?

If it wears out what will be the consequences (is it still safe to drive, for example)?

My car was/is mostly highway cruiser, no track use. Would that kind of use wear the differential less? Generally, how would one check if the differential is still operational?

 

None of my Porsches have a LSD feature, but I have owned other cars with one: '96 Mustang GT, '01 Camaro Z28; and an '06 Pontiac GTO.

Unless one is engaging extreme driving around town with hard acceleration in a straight line or around sharp corners in which one tire spins -- LSD is engaged or transfers force (torque) from the spinning wheel/tire to the one that is not spinning -- car diffs and their LSD feature are pretty robust.

For my cars with this feature (as with all cars without this feature too) all I did was to have the tranny/diff fluid changed at reasonable intervals using the factory recommended fluids/additives (some cars/models with LSD require a friction modifier additive).

As best I could tell in all cars the diff/LSD feature was still working just fine: The Mustang had over 120K miles on it when I sold it; the Camaro around 28K miles (in 5 months of ownership); the GTO 40K miles.

Now if you opt for an aftermarket LSD solution you'll have to rely upon the LSD maker for what is required in the way of fluids/additives and how often these need to be changed and when the unit should be rebuilt.

Oh, safe to drive? I would have to say 'yes' with some qualification.

Simple wear should be safe.

The side effect from this wear is the LSD would lose some to all of its ability to direct torque to the outer wheel/tire in a turn and instead this torque would be instead directed to the inner wheel/tire (same as a car sans any LSD) and over time this inner tire -- in the USA with right hand drive it is the right rear -- would/could -- it depends upon how aggressively one drives on the street -- wear faster.

With cars sans an LSD diff I have seen some cases where the right rear tire is at the wear bars some miles before the left rear. A worn tire is a safety concern.

Also, under some driving styles -- I would have to think at the upper end of what could be considered acceptable (and legal) driving on the street -- the car's handling at its 'limit' might be affected but it is the job of the driver if he wishes to engage in this type of driving to be aware of it and deal with it properly *before* he and the car end up around a tree or telephone pole.

Now a rear end -- with or without a LSD feature -- can always suffer some mechanical failure that can advance -- sometimes rather quickly -- to the point the car's handling and control becomes affected.

However, these types of failures generally give some warning and it would take I believe someone with a death wish to continue to drive the car with these warnings ongoing.

You are more at risk of having to deal with a tire blow out than a failed diff/LSD.

Catastrophic failure of the diff/LSD of a street driven car just doesn't happen all that often and when it does an accident is very very unlikely.

Always when driving you have be prepared for the unexpected, but failure of the diff is not an unexpected event I stay awake at night thinking about.

My unexpected events that I wake up in the night thinking about is red light running Volvo driven by some dumb-*ss on a cell phone or a sleep walking mule deer with a death wish. <Shudder>

Oh, how to test if the LSD feature is working?... I have nothing specific.

My WAG is absent any signs of distress -- noise, play, metal fragments in the fluid, etc. -- the thing could be considered working and thus if it ain't broke don't fix it.

Now there might be a test that could involve a chassis dyno (in the case of the Turbo with all 4 tires on rollers) in which the rollers (separately) of one axle (that with the LSD feature) could be unlocked from each other and from the dyno to simulate one tire spinning and observe/measure the amount of torque directed to the tire on the roller that was connected to the dyno and offered some resistance, simulating for instance driving with one tire on pavement and the other tire on snow/ice, as is common in areas where the snow falls.

As for some static test/check... and one that a home mechanic could do: I have no idea.

Sincerely,

Macster.

 

Check the 993 board for how to test if an LSD is working. Need a lift and spin each wheel while you look what is happening to the other wheel.

I had a factory OEM LSD on my 993. A twin disc, I think, and they do wear out.

I replaced mine at about 80K miles with a Guard. Solid, reliable, piece of art.

 

the oem diff in GT3's is known to wear out in a few thousand miles. Not sure if it's the same for turbos.

Do a burnout. See if it leaves two black marks or one

 

Thank you all, guys, you are all very helpful!

 

"It ain't wearin' out." Insert Georgia drawl from Porsche driving instructor.

I'd like to drive LSD TT & non in an environment where I can tell the difference. Since that rules out everywhere, but a track and it's not a track car- I doubt I'd see a difference.

 

Beautiful!