John McM

Teejae,

I had a noisy LSD after a transmission oil change and this is the post I put on the forum when I found the fix;

"Rang the OPC that serviced my car, and asked them what oil they'd put in my transmission. The reply was Mobilube 1 SHC 75W-90.

When I said that my LSD was growling, they apologised profusely and collected my car from home and changed the oil to a LS90. The noise disappeared immediately the oil was changed.

According to my Internet search, LS90 is recommended for all differentials, including limited slip where an API GL-5, GL-6 and BTR-41 gear oil is recommended.

I'm not sure what brand they used, but I also found the following Mobil product description: Mobilube HD LS 80W-90 provides exceptional chemical and thermal stability at elevated bulk oil temperatures. It's a special gear box lubricant designed to cover automotive gear box applications where limited slip oils of API GL5 and US Army Specification Mil-L-2105B specifications capable of withstanding extreme pressure are specified."

That should help you get the right oil.

Teejae

So my manual says to use 75W-90. I talked to the Porsche dealership and they said this was the correct fluid and there wasn't any additive that they used. I have already puchased lubricant, so I'm going to start with it. I'll see if it works, and if not, I'll try the Mobilube HD LS 80W-90. Has anyone ever tried any of the Redline lubricants? Like Shockproof or 75W-90NS?

viperbob

The Mobil 1 bottles say they are good for limited slips. You also have the correct weight. As I mentioned back towards the beginning of this thread, stop by a Chevy dealer and get a pint of limited slip fluid. This helps the fluid work even better and lasts longer with the limited slip. The cost is like $7-8. The nice thing is, this is finally synthetic. Until a few years back, this stuff was actually whale oil. No kidding...

cobalt

I had the same problem my mechanic added this additive and the noise went away after about 100 miles. I will try to find out what it is. He claims there is a bulletin out on this because Porsche had a lot of complaints.

Teejae

Thanks to all for the info. I picked up a bottle of Limited Slip Additive from the GM dealer and changed the fluid today. I still have grinding, but as per Anthony's 100 miles until it went away comment, I'm still holding out hope. The car shifts better now.

-Tarrnie

1994 black/black turbo 3.6 B&B headers/exhaust

John McM

Tarrnie,

Hope it works, I couldn't stand the noise when mine had the wrong fluid in there.

BTW: My noise went away immediately after they changed the oil, but the wrong stuff was only in there for a day so maybe that was the difference.

pss

Hello gents. I have the same problem, which I bounced back to the Porsche Dealer I bought the car from early this year. No result yet.
Teejae, how is your solution doing now? Still OK?
Txs!

Frank 993 C4S

Teejae hasn't posted in 8 years. Unlikely you'll get a response.

BTW - mine makes the same noise.

Flachbau

This subject is a true 'oldie but goodie' - threads going back over a decade - probably a record or something. I explained in a 2010 post. It is always there in reverse whether you hear it loudly or not. You don't use reverse enough to worry about it if that is when you hear it.

https://rennlist.com/forums/964-turb...sd-noises.html

pss

i also hear it driving forward when no force on the system, e.g. shifting gears from 3 to 2 and then cornering, first right only, now also left; all in normal, rather slow driving mode, nothing racy or bumpy.

Max964t36

That's not normal ...

pss

problem solved. Porsche Rotterdam replaced the diff under guarantee: nouse and 'bumps' in close turns gone. also hardly any noise going backward.