Option code for LSD in a 915?

[MotoSook]

Wil,

Can you explain how an open diff. would leave two rubber strips in a straight line? I'm not trying to beat a dead horse or keep the merry go round going around, but the post about leaving two rubber strips with an open diff has peaked my curiousity.

[Wil Ferch]

Souk:
No question that an open diff will bias the torque to one side...however, it's been mentioned a number of times here (as well as by magazine testers), that the extreme rear weight bias of a 911 will tend to mask the open/closed ( or shall we say.."semi-closed" ) differences in the differential.... that are more readily seen in front-engined, rear-drive, but front-weight biased cars.

So...yeah, as much as you'd expect one long stripe regardless of where the car's masses are located, the extreme rear heaviness might have you see two stripes even with an open diff. Or at least the *tendency* for that to happen might be more probable on a 911 than for any other car.

As I said....why quibble?...why not check tire rotation to see if the LSD effect is there..that was the original qustion anyway, right?

- Wil

[MotoSook]

Alright, the original poster could just jack up the car and test for LSD, but this is the first time I've heard an non-LSD car leaving two strips. I've got an E30 BMW with an open diff. and it will leave a single strip all day long. My '76 911 sans LSD will do the same thing. I've never seen it leave two strips, but I sense wheel spin (one wheel) on wet or dry surface in a straight line or corner. I'm not trying to be contrary, I just have never heard of this or read about it in the 20+ years that I've been a car geek. I guess I'm just non-LSD ignorant.

[Oh Haha]

Me again.
I have used the rotate one wheel and see what the other does method. They rotate in the opposite direction. For whatever reason, the car woulpd leave dual marks on the pavement on the 1-2 shift. I don;t speed shift anymoe so I don't know if it will do it now. I know that she came from the factory without LSD.

[xtr10]

what about if you spin one wheel and the other doesnt spin at all?

[sus911]

In that case, I would leave on the jack stands for a while....

[Goth]

I know someone said put it in neutral, but I think you need to put it in gear for the wheels to spin in opposite directions on an open Diff.

[dvkk]

Originally posted by Souk
I'm having a hard time believing that an open diff. will allow both tires to lay down rubber at the same time. Even on a perfectly level surface there will be an imbalance in the torque and grip at each wheel. When that imbalance occurs (likely at the initial application of power), the power will be tranfer to the slipping wheel (or wheel with less traction) and stay there.

You may think so, but in reality, most cars will not peg-leg in a perfectly straight line.

[fourteenten]

AT stands for Austausch, replacement....A bit late for the reply.

Cees