Mike Murphy

My guess for rarity is probably because it was expensive, like many Porsche options.

theiceman

LSD adative Pete ?

is there something I should know ?

der Mond

Ice,
With any LSD, as I understand it there are thin clutch plates that require a special friction-reducing additive to allow them to not stick together, which creates chatter. This is reportedly true even if using synthetic transaxle fluid. All manufacturers of vehicles that have LSD as an option stock their own additive in their parts departments, but I'm not sure that there are any major differences. I used a GM additive in my 911 that someone on Pelican recommended and it stopped the chatter when cornering. Maybe it's Teflon, who knows, anyone? At any rate, when you take a vehicle in for service on the rear end, the tech normally checks to see if it has LSD so he can replace the additive. Unless he personally uses LSD as an additive as some of us did in the 60's-70's, in which case it may be impossible to identify where that chattering sound is really coming from... =)

theiceman

hmmmm

I have LSD and just used swepco without any additional adative, corners great ( especially on the gas in the wet ) and I have no chatter .. am I just lucky ?

der Mond

Perhaps the Swepco has an additive in it as a Redline product does. I thought Swepco was better for the older transmissions, and Redline or Mobil1 was preferred for the G50?

theiceman

would make sense since I have a 915... hey I am not gonna nock it ... :-)

Mike_ONeill

I have an 83 911SC. So to tell if I have the LSD, I jack up the rear of the car and turn one rear wheel, if it has LSD the other rear wheel should also turn. If it does not have the LSD the other wheel will not turn?

Edward

Hi Mike,

Kinda. The quick way to tell is if you turn one wheel by hand, if the other spins in the same direction you have an LSD; if it spins in opposite direction, you've got a normal open diff.

BUT, this is not a definitive test as it can lead one to believe that you have LSD. My 993, for example, does NOT have an LSD and the tires will spin in the same direction when one is turned by hand ...I was told that the spider gears may be "tight" or dragging a bit (but not a cause for concern according to them ...hopefully). OTOH, my SC Trackmeister does have it, and the wheels turn in like direction. From what I understand, the real test is disconnecting the axles and applying torque to one end and measuring the difference.

Edward

Edward

BTW, to Pete and others with LSD knowledge,

I've read for some time that the OE LSD plates don't last all that long. Is there a decent road test I can do to assess it's functionality. FWIW, it "seems" like my LSD is "interacting" in 3-pt turns. So I assume that with the steering going full lock, the drastic difference in radii betwn the L and R drive wheels makes those parking-manuvers feel a bit "odd" or otherwise not normal ...don't know how exactly to describe it, but does anyone else feel what I am describing? FWIW, this is my trackmeister, and the car feels really planted and neutral in tight, 2nd-gear turns (going in as well as powering out). Zero understeer unless I induce it. But how else may I "test" the LSD? Maybe on the wet skidpad (which is offered on occasion)? What would I "look for," push under throttle? Thanks!!

Edward

Roc Doc

That's my situation. My '76 915 has one, and it won't lock up under a hard load, (tight corner), but you can feel it a little in a sweeper if you jump on or off the throttle.

Ed Hughes

I've got it, and it's working well...try running a spare time on LSD, it's not fun. Of course, that was when I could run a spare. Now, I'm hoping I never have to use my can of Fix-a-flat.