Kolbjorn S

Hi everyone,
a week back I posted a message regarding front-end noises I heard from my shark. I checked the useful advises I got - ROG100, okbarnett, Mark and Gretch, many thanks for that - but feel a bit stupid as after careful listening (together with the always helpful service advisor at the local p-car dealer where I bought the car), actually the noises originate from the rear of the car. And, I believe it is the LSD, meaning it is not an unusual noise at all. Can you guys confirm that the LSD is supposed to "grind" a bit when you start the car, and drive off in 1st (or reverse) while turning? My only experience with a LSD car is a friend's GT3 I test drove, and on that the noise/grinding on take-off was absolutely extreme.

From a search, I found one post (third reply down) explaining a similar situation.

Interestingly, the noise / grind / shutter only appears after some driving, i.e. when the transmission oil has heated up. Is this normal as well?

Jim R.

I don't think so. Mine is pretty quiet. Have you checked or changed fluid? Maybe a switch to synthetic gear oil will help-it is a relativelycheap fix.

Jim R.

Gretch

Mine is quiet also...only time I know it is there is when both tires are smoking............

Jessa

Nope, no ginding unless I doing something cruel and stupid with the transmission.

atb

Should be dead silent if working correctly.

Probably just needs a fluid servicing.

If someone filled your differential full of NS oil, that could definitely be contributing to your noise.

ColinB

Mine's quiet.
NB. Before you do anything else change to Mobilube 1 or equivalent fully synthetic transmission oil. It might not be the solution to your problem but you need it anyway. It transformed my gearbox.

Colin 89GT

jpitman2

mine is quiet, but its an auto. I can feel it catch spin sometimes if I give it too much on wet road, but dont hear it. I have seen and heard Jeep LSDs make nasty noises, but they went away with a change of oil spec.
jp 83 Euro S AT 48k

Kolbjorn S

Thanks everyone, I will change it to Mobilube 1 (the one used by the P-car dealer by default) and let you know how it goes!

dr bob

Remember that the limited slip clutches only move when you are going around a corner. If you have the wrong lube in there, the clutches may 'chatter' a little as you go around slow corners. That's the only time!

If you are hearing grinding noises at any time, it isn't the LSD unless the ring-and-pinion or a bearing is going bad. Either requires a teardown/rebuild of the diff, and more if you have an automatic.


First step is to pull the filler plug and see what the oil level is in there. It should be very close to the plug level when on level ground or raised up level. If it isn't that full, or if you see metal bits or any silvery stuff in the oil, you'll want to drain and catch the oil as it comes out to see what's in it. Anything more than a small amount of LSD clutch material is cause for alarm, and a good reason to pull the rear cover from the housing for a full inspection.

Good luck, and let us know what you discover.

Kolbjorn S

Hi guys,
well, the new Mobilube 1 oil is in, done at the P-car dealer, and I was quite surprised to find that the noise / shutter got worse ...
To be specific, previously I heard it only upon take-off while cornering - now after oil change even at slow-speed (being 5-10mph) but only while cornering obviously. Other than that (i.e. faster) and it's dead quiet. Shifting is just beautiful.

The quality and level of the old oil (type unknown) looked fine, and the magnetic part of the drain plug did not contain any metal or debris at all. No leaks. Nothing seems wrong according to the mechanic.
I wonder, is my LSD the same as the one you GT guys have...? My S4 is an early production (12/86).

In search of the perfect lube ....

dr bob

There are "friction modifier" additives specified for clutch-type LSD units to allow for less chatter when cornering. Places like Pep Boys have that stuff where they sell the gear lube. This might be an answer for you. Stuff is required in Ford cars, for one example.

Brent 89-GT

I have never heard mine make any noise. I can feel it working on tight low speed corners, but I can not hear it.

Porsche does not require a friction modifier for its LSD differentials. I would not add this to my car as the the transmission and differntial share the fluid and I am not so sure friction modifiers are good for the synchros in the trans.

I have to wonder if there is a bearing going bad in the trans causing the noise. It shouldn't make noise, especially a grinding noise. Must be pretty subtle if the Porsche tech thinks all is well?

Jeff McVicar

I'm paying close attention here becuase my only experiences with lsd was an oral dose.

okbarnett

I think the LSD is as quiet as the non. But the dealer said it is normal. If you are hearing something , I think there may be a problem somewhere none the less. Its not the kind of oil you used. They may not be paying close attention. It could be a diff clutch or cv joint or bearing. This is a 15 yr old car. And also with the lsd you get a lower ratio gear, so it feels more responsive then a non lsd car.

Sab

I have a slight "chatter" or vibration if I take off at a radius from a dead stop. I was told before that this is normal for cars with LSD, but I didn't beleive that. I didn't know that the transmission and differential share the same fluid, I thought that was seperate. I asked for my differential fluid to be changed a while ago and did not feel any vibration at all for several month, but it then came back. I never heard any noise though.
regards,
Sab.