Ducati998

I recently purchased a 1987 930 with 55K miles. I have wanted this car since I was 8 yrs old, but as a first time owner I have some serious learning to do. I had a PPI done on the car by Vertex in Miami (who came very highly recommended) and they missed a ton of stuff. The most concerning oversight is that when pulling out and turning the rear diffential makes a rubbing, crunchy sort of noise. I was told by the mechanic who missed this issue that the car probably has the wrong diff oil and it just needs changed. I saw the potential of the car and pulled the trigger in spite of the issues.

I am a pretty competant amateur mechanic when it comes to working on my bikes, but have never wrenched on a Porsche and have never messed with any differentials beyond replacing the oil. I could really use some insight from some of the experts who reside on rennlist.

Is this a common issue?
Does the diagnosis sound accurate?
What is the best diff oil to use for a 1987 930?

I have other issues that I plan to post on seperate threads, but if anyone has any experience with diff issues, I would really appreciate some advice.

Thanks in advance!

P.S. Is it ok to post pics of your car? Not sure about forum etiquette.

theiceman

pics of the car are Mandatory Welcome to Rennlist . There are a lot of Carrear guys here who can comment but i think the turbo had a different gearbox. The guys on the 930 forum would know for sure .. and vertex came highly recomended ? Wow...

i am sure they are still in that little hovel at 39th. I know its an older car but i am sure the collection would have done a PPI . That car there looks to be a collectable .

Congrats.

Amber Gramps

Welcome to rennlist.

I'd start my search for answers with the CV joints and wheel bearings. Much more common issues and easily missed on the PPI.

ivangene

sweet ride!

diff swapping is serious business getting the gears to line up correctly takes knowledge and lots of shims, some time and knowing what you are looking for with regards to gear mating

I would suggest the wheel bearing check as well...I am doing one right now. Mine did NOT make a bearing noise but rather a grinding sound like I had no brake pads when I would load the car in a turn. but was random and hard to detect where it was coming from....turns out it presented itself....

also could be as simple as a loose axle nut....have that checked too (its like 300 ft pounds or something)

whalebird

4 speed 930 is a major RUSH, I like them over a 5speed myself...that's a beautiful car. Get a second opinion on the diff. 930s have a different wheel bearing configuration than a 911 and they are a bit more problimatic than the 911 and replacing them is a bit more involved. I would look at that first. Change the fluid in the trans noting what comes out(look for metal pieces) as this may help in diagnosis of a transaxle issue. Replce with a GL-4 like swepco 201.

Mark Salvetti

I'm wondering if you have a limited slip diff, and you are hearing it chatter.

911/930's have transaxles; the differential and the gearbox share the same gear oil. Your 1987 has an older transmission with steel syncros; I think most people are still recommending a good non-synthetic gear oil like Swepco.

Jack up the rear of the car, release the parking brake, and rotate one of the rear wheels by hand. If the opposite side turns in the same direction, you have an LSD. If you do have an LSD, the gear oil needs to have an additive added to prevent the LSD chatter. That may be your problem.

I read somewhere that the Swepco already has the additive. Since you really don't know what's in there now, or how old it is, you could change your gear oil anyway just for peace of mind, and see what happens.

Mark

irobertson

Welcome!
Great looking car!
Ditto what Mark says, I'd start by making sure it has the right lube before jumping to any conclusions.

cheers

Steve Weiner-Rennsport Systems

Mark offers sound advice.

You may be experiencing something called "stick-slip" with the LSD and that requires an additive to fix. These transmissions are picky about what gear lube is used and that may be the root of your problem.

Amber Gramps

The option code is 220 for the 40% LSD. If you do the fluid change yourself and you do have an LSD, remember that the additive stinks to high heaven. You will not want to spill a drop.

....and that has got to be the sexiest car ever posted on rennlist.

RShepHorse

I had this with my LSD when I first got the vehicle. It was a very noticeable shudder/noise when making sharp turns, especially if I had been stopped i.e. pulling out into traffic. Changing out the diff oil and more importantly adding the correct additive completely fixed the problem.

Ducati998

A sincere "Thank You" to everyone! This is the best site that I have found. The wide array of responses prompted me to buy a two yr membership to rennlist and pick up some Swepco 203 and the GM Limited Slip Axle Lubricant Additive today. I am hoping that I can cross one of my issues off of the list. I will keep you posted. Thanks again!