password

The LSD in my 944 (new car) makes some chatter when turning tightly. You can really hear it and feel it. Is it normal to make some noise when the wheels are starting to slip? Going straight no noise and shifting is fine. Slow turns when I am gently on the gas it makes very little noise, but if I hammer it, it makes that chatter noise while working.

I just changed the fluid to redline 70-90 NS and added in a friction modifier. I can add more modifier, but I don't know if some noise from the LSD is normal.

Thanks

83 944

95Juan

'83 w/LSD?

are you sure it's not CV joints?

password

Positive. The axels were recently replaced.

When I first did the fluid change it chattered just going forward. I added @ 4oz of friction modifier and it smoothed it out that it only happens on tight turns when the wheels break free. I just don't want to add too much friction modifier if I don't have to.

kasturbo

Doesn't the Redline fluid already have the friction modifier in it?

password

I used the NS.

Oddjob

When you say "chatter", is it one the rear wheels slipping/hopping, or is it an internal transmission noise?

An internal noise is not normal for a properly functioning LSD. And not sure that would even be typical for a failing LSD.

If the stock LSD friction plates are worn down, I am all but sure it will slowly allow more and more slip until it is not limiting the slip at all (functions basically as an open diff). Im not sure if anywhere along the wear/life cycle of a clutch type LSD, that a chatter type symptom would ever exist.

Wheel spin/hop would also be a little unusual for stock factory 40% locking LSD, which is basically unnoticeable when driving. It allows enough slip, that when making tight turns the inner rear wheel will not hop (since the diff is still allowing enough slip for the inner wheel to turn slower than the outer wheel).

If it is hop, that means the diff is locking the rear drive shafts so that the inside wheel will momentarily spin to catch up to the outside wheel, creating a "slip-stop" effect. So the wheel will spin for a split second, catch for a split second, then spin again - through the turn/corner. If thats the case, I would think that is indicating that the diff is locking "too" much, or some really dried out tires (which are generating less traction than porsche expected from stock/original spec tires).

I have heard various different ideas about using different trans fluid brands, synth, non-synth, with additional additives, etc. Some say straight synthetics are too slippery for synchros and clutch type LSDs to work properly, and others have not had any problems...

Any noise or problems before going to the Redline, do you know what fluid was in it before?

password

I don't know what fluid was in it before. I know that the fluid I added had no friction modifiers, and so I added Friction Modifier 1oz at a time to stop the chattering. It has almost gone away, but you still feel it as it is slipping. The wheel doesn't hop, The tires are new. If the factory LSD should really make no noise at all I will just keep adding a little more FM until it quiets out.

bald_joint

just go to your nearest GM dealership and ask to the parts/service dept. for Friction Modifer Additive.

Unscrew the plug the differential nut and add the half of the bottle, arround 125Ml if my memory is good. Go in a empty parking lot and turn in roung making 8 shape for 5 minutes. It should completly disapear, and if it still chatter, put the rest of the bottle. The additive should stay active for a good 25K miles... Miracoulous for a 8$ stuff...

For once it dosent cost much to repair our 944 !!!