Locking differential and limited slip are two different things.

Limited slip allows the wheels on the same axle to rotate at a different rate, such as when turning, the inside wheel has a lower RPM than the outside wheel, because the inside wheel in carrying less distance. In a street car, differentials are forgiving to allow for slip, but the more "open" a differential is, the more power is distributed to one side (the pinion side of the differential). But if that wheel doesn't have traction, the power exerted to that wheel will be lost in spin. the account for this, cars have "limited slip" differentials, which do exactly that.

Locking differentials force both wheels to spin at the same rate at any condition, even the car is turning, so while one wheel might be covering less distance than it's opposite, it will be forced to slip. Common in rock crawlers where friction against wheels varies, and in drag racers where the car needs even distribution in power to stay straight.

 

I think you guys are confusing terms a bit. A full time locked differential (like a welded diff, or a spool) requires both the left and right wheel to spin at the same speed all the time. About the only time this is a good thing is drag racing. As pointed out earlier in the thread, when you make a turn each wheel takes a different path. The outside wheel will have a larger radius than the inside wheel, so it needs to turn faster. If you want to go around a corner a full-time locked differential is not a good thing.

A "limited slip differential" allows a slight difference in speed between the two tires to account for this. It also channels torque to the wheel with the MOST traction. That's the primary advantage.

A standard "open differential" also allows the wheels to spin at different rates, however it channels torque to the wheel with the LEAST traction. Typically if you start spinning one wheel, all the power will be channeled over there. That's why you see the "peg leg" one wheel burnouts from cheap Mustangs, Camaros, and Hondas. If you've ever heard a muscle car guy refer to a "Positrac" that is an example of an early locking differential.

As far as the "locking rear differential" in the 911 I haven't pulled out the factory service manual and verified every gear and shaft in the thing, but it sounds like it is an electronically actuated locking differential, as opposed to a full-time locked diff. That would allow the computer in the car to lock the differential under hard acceleration and leave it open otherwise.

Quaiffe is one of the best known Limited slip differential manufacturers for motorsport, they have a pretty good explanation here. http://www.quaife.co.uk/differentials

 

Great explanation +1 but I think the OP wanted to find out how to prove that his car has LSD ....

 

not feel'n the love...

 

:-) Help me, what does that mean?

 

I got a little carried away in the description of the different differential types. I think the answer isn't very satisfying though.

Given that it is a mechanical lock that is electronically actuated, it would only be locked when the computer wanted it locked. I doubt the standard jack the car up and spin the wheels to see what happens test will work in this case. I'm interested in this as well as my car has the same option.

 

I actually added an LSD to my Z06 as it was a decent adder ($$$) when I upgraded my differential and with 800 FT# of tq I thought it may be a good idea.

When you take a turn hard the wheel that has the most pressure applied to the road (inside wheel) is well planted and will not have a tendancy to to break loose via the torque put out by the engine. However, the outer wheel as the weight is removed will start spinning as the torque from the engine finds a point of release. An LSD will stop this from occuring by balancing the torque automatically. In otherwords, the torque is applied to both wheels equally regardless of where the weight of the car is placed.This transfer of torque is automatic but is progressive so that the outer wheel does not just lock up but rather slowly balances the torque so one does not loose control or even notice the transfer of torque is occuring.

I hope that is understandable

 

exactly as above..it is a wheel torque transfer system on the rear axle (mechanically engaged) based on consistent wheel spin monitoring of either wheel )via PCM.

 

But LSD also has benefit under deceleration as it helps prevent lift throttle oversteer 911 tail over front syndrome) is a bit more controlled as both rear wheels are acting together when engaged and like somebody else mentioned it helps in controlling a "drift" or what is affectionately known as a "power slide" around track corners...

 

Needs to be re shimmed. Porsche uses friction plates and a spring washer to pre load the friction plates. About 800$ for rebuild kit.

 

thanks for clarification, after i read it , i am like great but still doesnt answer my question

 

People are still posting confusing locking diffs, LSDs, and open diffs also .