LSD will turn both wheels in the same direction.
Open diff will turn both wheels in the same direction only when in gear

If I recall correcly ...

 

IMHO, friction modifiers or additives should never be used in transaxle combos unless specified by the MFG. I must admit, I don't know if Porsche ever speced a friction modified EP lube for the Mecedes trans or not. Hmmm.... If it were me, I'd go with the best EP available and be done with it.

My Mondial has a LSD transaxle and they spec a simple 75-90 Hypoid gear oil with no friction additive. Be safe, or buy gears later.

 

Nope. Opposite direction, the torque is running the spiders inside the diff with the ring gear stationary.

 

\
I am pretty sure that 12 designates LSD.

 

Ok, I just got back from doing some assorted burn outs on a dead end road. The road wasn't quite wide enough to do full donuts, but I did get in a bunch of harsh zig zags and some half circles.
This is what the rubber patterns were like:


I had my windows down and could hear each wheel start burning out when it began to lose traction. They would spin on one side and then on the other. LSD?

BTW, that was heart pounding!

 

Kid in a candy store huh

 

Better! It was in a real quite and peaceful valley; you could probably hear it for miles. Too bad a rmb can't be hooked up for the 86-....

 

John -

I think that in an insanely outside-the-bell curve situation, you could have an LSD that is so utterly worn, that the plates are not even grabbing each other, and in that case, it COULD be that you have an LSD and it really needs new parts, but that is so highly unlikley, etc.

Now, that said, my reaction to your burnout story is to simply do more. It sounds fun, and I do it often in my S2000. For some reason I never really did with my 928s, until one time I felt the need to, and dumped he clutch in the 86 at about 5500rpm. That was two solid stripes for about 30-50 feet.

Is it hard for you to take the bolts off the back since you would want to know what fluid to use? That way it will be a total fact either way. An LSD looks a certain way and an open diff looks another.


That said, I think Zeus is right.

 

Brendan,

I just replaced the oil, but it could be carefully drained and put back in after opening up the cover. Part of the reason for replacing it was to see if it would have an effect on the growl noise that I occasionally hear when in 2nd gear and accelerating from 1,400rpm; it very slightly does it in 1st sometimes. It didn't occur to me that the noise might be the lsd until after the oil change. Then, I was checking the option code sticker and saw no options listed, which was odd. Then, I did the wheel test, which was surprising because the car has always responded like it has lsd (from the descriptions on rennlist).

After doing the zig zags, I noticed that the growl effect would come on a lot easier (from heat maybe?), so now I'm thinking there are worn lsd disks back there that is causing the growl noise. Either way you're right. It needs to be opened up and looked at.

If it does have lsd, is it difficult to replace the disks? (does the transmission have to come out).

 

Sounds like classic no LSD to me.

BTW yes the PSD acts like an open diff until it is commanded to do something - e.g. it detects wheel spin or certain combinations of relative rear wheel speeds & lateral accelleration - only then does a variable hydraulic pressure activated clutch engage for slip control.

Alan

 

to be a slip it would have a 12 in front of the trans number then as of 1988 the 5 th number of the trans number is 0 no dif, 1 normal diff , 2 slip.

 

My LSD generates solid black 11's and rear completely slides out from under me on dry roads. Do a hard U-Turn and stand it it completely halfway through it. If you are fighting to get the rear end back under you and generate solid 11's then you must have a working LSD. Also once the rear end is completely to the side, let off and as it sweeps under you hit it again and it should swing violently to the other side and hold it hard until the fish tail settles down. You should only see one break in your 11's.

Cheers,

 

With Jim's comments, its all more of a mystery, as LSD could be added after the production of the car. 20 years is a long time. Its a trans-out process if you enjoy your sanity. I supposed it could be done with the trans in the car, but all that work is easier on a table.

Its all just bolts I like to say.

 

Andre - I think you must be trying too hard.... or need wider tires

Once both wheels loose traction the LSD/PSD or lack there of isn't going to make much difference until you get at least one wheel hooked back up... only then will you really be able to tell a big difference.

I think its intuitively easier to tell whats going on by provoking just 1 wheel to slip - pretty clear what is happening then... incl. whats slipping.

e.g. 1 wheel on dry pavement & 1 on slick wet or pavement & dirt (accepting the dust cloud).

Full dual rear burnouts... well I don't know about you but I'm not all that practiced at telling exatly whats going on.... except that I don't get to launch very fast that way & I can feel & hear the tire dollars dissapearing!

Alan

 

very, very few 928s have had a slip added...and no one knows that better than I do About the only ones to add a slip are track junkies and the total number of tracked 928s is no doubt a two digit number.