SeanR

If you've got a one wheeled wonder (non lsd), one tire will spin and the car will continue to go straight through the turn. LSD, your *** wants to swing out if you loose traction.

Leon Speed

First rain is always tricky. Oil/dirt/sand floats on the road before it washes away.

RFJ

+1 what the man said.,Ray

Larry Velk

In the old days in the great white North guys didn't want "posi" because on a crowned country road the car would slide to the swail if both wheels spun. The physics - a spinning wheel is in kinetic mode, where the coefficient of friction is (typically) less. A wheel unpowered ('peg-leg') is not spinning and in static mode - hence higher "mu", or friction coefficient. This wheel tends to hold against side to side thrust and keep the car from sliding down the crown. The coefficient differences aren't that great, but enough to make some difference. This is somewhat conterintuitive, but think of turning wheels - they are stationary wrt the road.
We drive our 928 in the winter and I'm glad we have 'posi'. We know the form in winter driving and would rather have "two turnin' rather than one burnin'".

SMTCapeCod

Do you know what is in there to begin with (fluid)?

Perhaps it makes sense to try adding some limited slip additive to what is in there, see if it has any effect on the 'chatter'. Of course if its judder- tires skipping sideways..then shocks might be the right recourse. Maybe yours was just mocking one of the 911s...

Then hone in on the right answer regarding NS/non-NS and fill accordingly. I used to know...now it escapes me. NS is less slippery, I thought, hence its use in the Borg manual transmissions where the additional friction fosters better synchro action.

928mac

Remember that your 89 will have more power as well.
My automatic will kick over a foot on dry pavment when it shifts from
1st to second at full throttle.
It has got me sideways a few times, but you get use to it. Kind of fun.

Pagnobito

My previous S4 had an open diff and would spin up one wheel and not really get sideways at all, then I had a LSD fitted and the characteristics changed, it would quite easily get sideways but you could control the slide with the steering and power, great fun in the wet. In the dry it was fun to leave two tyre marks on the road off the lights.
Turning slowly you do get chatter, it is just the way the mechanical LSD works. The PSD system doesn't do this.

jheis

I have an email request into Red Line & will post whatever I find out regarding their current recommendations.

James

Brett928S2

Hi JAMES

Ignoring the option code (diffs can be changed by PO`s) and ignoring the chatter...have you jacked up the back to spin the wheels to actually KNOW for definite its got an LSD ?

The reason I say that is that what you describe is exactly the sort of effect i used to get at junctions in the rain in the UK...when I didnt have an LSD....

Now i have an 8 plate i just power both wheels if I wish to...

And no "chatter" not ever with my LSD...

Personally I would jack up the back and check first..

All the best Brett

jheis

OK, here's what Red Line recommends:

"James,

Thank you for contacting Red Line Oil, some time ago we used a fluid blend in the Porsche transaxles to closely match the original. The 75W90NS now contains a slight amount of friction modifier, for improved shiftability not for chatter control.
In your 928 transaxle the 75W90NS is recommended, if chatter is present from the clutch type limited slip when making a slow/tight turn a slight amount of Friction Modifier can be added, being aware that excess will adversely affect shiftability. Typically Porsche limited slip differentials don’t chatter, if chatter occurs 1 to 1½ % would be a good starting point. The 75W90 contains 5% friction modifier too slippery for the synchros so not recommended for use in a manual transmission/transaxle.

Regards, Dave
Red Line Oil"

So, 75W90NS it is with maybe a splash of friction modifier if the chatter doesn't go away on straight 75W90NS.

James

James Bailey

Actually.."it would quite easily get sideways but you could control the slide with the steering and power, great fun in the wet. " the same is true in the DRY if you try hard enough You can make a 928 drift !

Gary Knox

Sean said: 'If you've got a one wheeled wonder (non lsd), one tire will spin and the car will continue to go straight through the turn. LSD, your *** wants to swing out if you loose traction".

The only 928 LSD I've had experience with is the PSD on my '94. There are quite a few intersections on hills around here, and a good bit of rain. Never had the rear end kick out, but the PSD light comes on essentially every time. I have Michelin PS2's on the car.

I do occasionally lose a bit of traction on the inside wheel of the '89 S4 at full throttle in 3rd on one track in a corner that's banked pretty well, but also steeply uphill, and the left wheel is on concrete, while the inside one is on blacktop. Rear doesn't kick out there (dry track).

dprantl

PSD I think is smarter about this. From the demo videos, it seems that PSD will try to keep the car stable during a turn instead of letting the rear slide like with a conventional LSD. Having driven an '86 for 8 years with LSD and comparing it now to my GT with PSD, I can verify this is true. With the same tires, the '86 would kick the rear out in the rain very easily, but with the GT and 70% more power and a huge amount more low end torque, it is much harder to do this.

Dan
'91 928GT S/C 475hp/460lb.ft

jbrob007

James, I have an 86.5 with LSD and it chatters some... I've already changed to Redline - 3 parts 75W90NS / 1 part 75W90... Easier to get into gear when its cold and shifts much smoother, etc, but still has some chatter - not sure what the fix is if there is one...

blown 87

Mine does not chatter a bit, I have redline NS and a couple of tubes of BG gear additive in it.
It also can exhibit throttle induced oversteer in turns in the first couple of gears.