[sparky]

When I purchased my car it came with a separate used LSD. I had it fitted by Porsche and it works fine at speed, but makes disturbing noises and grabs at low speed and tight turns. For example one tyre will drag and squeal briefly when doing a three point turn. <img src="/forum/images/smilies/968/unsure.gif" class="smilie" alt="" />



It almost a year since it was installed and the problem (if it is) has been there since day 1. Car does tracks work and recently did 1000km tarmac rally, all with no problems at speed (LSD works a treat). So its going strong.



I "think" its a torsen style diff (40% locking) but am not sure , it may be a "plate" type for all I know (i know I should have looked when it was loose). Various opinions from people who should know are generally "Don't worry - that's normal". But it just don't sound right to me. The noises are as if it is indeed a plate type LSD, e.g. sounds like scrapping plates when turning right angle corners at 40km/h. Its worse after a long drive.



Wondering if 968's fitted with torsen stye LSD's normally make such noises while healthy ?

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[flash]

it sounds like a locking diff, or a clutch type that is stuck or, at least set up stiff, to me too

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[rustech]

IIRC, if you lift the rear of the car, and turn one wheel by hand, the torsen type turns in the SAME direction while the clutch type turns the opposite direction like an open diff.



If you do a search on the various forums, I've read it is completely normal for the torsen type to drag wheels on tight turns. I would not be concerned but would read the search results.

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[wjk_glynn]

[quote name='rustech' date='Jan 1 2006, 11:28 AM']IIRC, if you lift the rear of the car, and turn one wheel by hand... the clutch type turns the opposite direction like an open diff...[/quote]



Nope, that's not correct.



Assuming the car is out of gear (or the clutch is depressed), turning one rear wheel by hand will cause the other rear wheel to turn in the same direction (i.e. if you turn one wheel in the "forwards" direction, the other will turn in the "forwards" direction) on a 944/968 fitted with a clutch-type LSD.



A clutch-type LSD connects the two half-shafts together via a clutch. They will turn together in the same direction until traction conditions cause a torque differential to exceed some threshold, which in turn causes a difference in speed between the half-shafts - hence the term "limited slip"



Karl.

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[nissanite]

This is common with clutch type LSD's. GM sells a limited slip additive that usually solves this. Better is RED LINE synthetic. Get the correct oil & this is the fix

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[nissanite]

Sorry, forgot to add the way to get the oil to the clutches. Put the car in a full turn, driving with no throttle, only enough to keep the car rolling, then change directions & do the same thing. Keep switching. The key is to not add power while circling.

If the install was done with a new LSD & not broken in, might just need this procedure. Happend to me on a race car once.

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[gbarrier]

I agree with the oil change. Use a good GL5 or GL4 with some addative. That shutter tells you that your lube is shot.

'

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[sparky]

OK.... the oil the Porsche Technician used in my diff is Redline "Synthetic Lightweight Shockproof Gear Oil". I couldn't see any mention of GL4 or GL5 on the label but reading the usage description it seems to be the right stuff? (the 968 user manual nominates GL5).



Also I've only had the car 1 year. It's a competition car so not many kilometres in the year, but hard ones.



Is this the right oil? How long does diff oil last?

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[Greimann]

According to Redline, the data looks OK, but, there is a disturbing paragraph in the tech literature that sounds like a warning:



"....but if further improvements in efficiency are

desired, and durability is not a major concern,

LightWeight and SuperLight ShockProof™ can be

used."



The durability statement is worrisome. The data sheet also does not mention anything about a GL5 rating and that is important for longevity. They also get funny with the viscosity description and that may be a source of your chatter. They say the Lighweight oil is akin to SAE30 motor oil. Here is the link to the data sheet.

http://www.redlineoil.com/whitePaper/11.pdf



If you want the maximum life out of the gearbox, then get a GL5 rated oil. If you plan on regular rebuilds, then this stuff may unleash some horsepower that is absorbed by a heavier viscosity.

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[sparky]

Very interesting stuff. I'm not into rebuilds - so I'm thinking I will replace the oil with Redline's 75W90 / GL5 product, this seems to be the right choice, especially as that's what the Driver's Manual stipulates.



thanks Greimann !

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