wwest

A "virtual" LSD, reactive only LSD, is inclusive with PSM, as it is with almost all modern-day vehicle stability systems. Uses differential braking to quickly abate wheelspin/slip.

wwest

That test only applies to one specific type of LSD, one which Porsche has never used to my knowledge.

wwest

A viscous based LSD relies on HEAT to stiffen, the more HEAT the more STIFFNESS!

Fluid is inside a hermetically sealed FIXED volume, since it CAN NOT expand with heat it effectively become more dense.

Goes from 5w to 90w viscosity.

Wayne Smith

I'll believe you. I had a locker on my old ****** but when I got a front wheel in the air slow climbing a hill it would spin independently of the other side (no front wheel drive). The posi on the rear actually performed better.

wwest

Since it is inherently dangerous, HAZARDOUS even, to have LSD on a front drive system it isn't often provided, not even for off-road vehicles.

You want to experience SEVERE torque steer, try one with.... but keep your thumbs outside the steering wheel.

Virtual front LSD's mostly brake BOTH front wheels to abate this problem, called TC, Traction Control.

Wayne Smith

Good points.

Back in the day all 4 wheel drives had transfer cases and hubs that you locked in at each front wheel. Fast driving was two wheel drive. Slow stuff that had you balancing on three or even two wheels (or up to the windshield in muck) was for four wheel drive. We used posi or lockers at both ends to get through. But that doesn't hold today unless you're on the Rubicon Trail or its equivalent. That is not 911 territory!

Talking about all wheel drive these days is from a completely different vantage point.

As far as keeping your thumbs outside the spokes, that's a given that I've seen too many people not understand. I haven't experienced it in years, but I've had more than one time when a tire caught and if my thumbs had been I the way I would have lost them to the steering wheel. One of those times was at under 5 mph traversing a hill when the front end decided to slide. You simply don't see it coming. Today's power steering mostly overcomes this, but ...

wwest

Yes, it's long past the time that the industry develop some terms more descriptive of what the customer is getting/buying.

R/AWD vs F/AWD, rear biased vs front biased, just a start.

4WD or 4X4, both part-time, should only be used as it was meant, defined, 30 years ago.

VC, Viscous Clutch/Coupling never was really functional, and now with PSM/VSC/TC those are totally useless, unless there is an "OFF" function.

Windyrun

thanks for the link, but when I tried it I get a blank page. When I google it the reply asks for login id. Am I missing something? Thanks

ltcjmramos

You're right. I just tried it myself, and all I'm getting is a blank page. I recall I had a similar problem when I was originally pointed to this page. Unfortunately, don't recall how I resolved it. I'll see if I can find the solution.

speedracerf4i

I just purchased 2009 C4S and was wondering if my car had a limited slip differential. I think that I found the definite answer to this question Per 2009 sales brochure, all 4 wheel drives 997.2 came with a standard LSD.

2 wheel drive models must have 19" wheels, I assume an C2S to order it independent of PASM or SPASM.