I have roaring sound coming from the rear of the car. It changes tone with speed but is otherwise constant regardless of throttle, gear, accelerating or coasting (gets a little raspy near stall). We put it on the lift and checked the hubs and prop shaft - there was no play. So we ran the car up to 40mph on the lift to listen for the source. Oddly, the car was quite from the outside, but the driver said there was still noise inside the car. We then tried getting up to speed and letting it coast down in neutral to reduce exhausted noise. There was a faint noise from the diff. With the car off, we spun one tire and determined the LDS is completely gone. Changed the fluid and found some small bits on the plug magnet (presumably LSD clutch bits). Based on this diagnosis, I plan to have the diff rebuilt and likely change the ring to 4.44 while I'm at it.

Here is my question for the racing community.
How likely is the LSD the source of my noise and how benign is this? Or is more likely a bearing that could lead to something more serious? I have an HPDE event at VIR in 2 days (no refunds at this point). Of course I'd prefer to go, but 1) I don't want a small problem to cause a more expensive problem than my already-planned rebuild, and 2) I don't want this to be a safety problem (rear seize at an inopportune time). If I'm just dealing with noise and an open diff, I'd like to run.

Your experience and insight are appreciated.

 

Most likely ring and pinion is on its way out

 

if your diff blows you'll need to tow it home...
if your diff blows you should be able to coast back to the pit depending how far pit in is...

 

See if you can credit the event towards a future event?

 

Thanks.

Go play:
I trailer my car, so towing isn't an issue.
I plan to replace the ring anyway.
No refunds this late.

Stay home:
Unlikely I can coast in on a 3.25 mile track with lots of elevation change, but that's always a risk.

Has anyone ever heard of a waning S2000 diff grenading, seizing, or doing anything that would be a reason to stay off track?

 

buy a spare diff for this event / future events?

 

I'd call them and try to work out something like this. You don't want to be that guy that they have to black flag the session for when the thing he knew was going to fail finally failed.

Alternatively, do you know any other local S2000 owners you could borrow/rent a diff from for the weekend? Diff swap isn't the hardest thing in the world.

 

This guy. This guy gets it.

Be courteous to the people sharing the track with you, don't waste their time if you have a high likelihood of having a mechanical and black flagging the session. I'm sure the track organizer will allow you credit, worst case scenario sell your spot to someone else.

 

I personally would not go and run the event. I don't ever feel comfortable running a car at high speed with a mechanical issue such as you describe. It's low likelihood, but what if it breaks and locks the rear at the worst possible time and you go off in a high speed corner and hit a wall? If at all possible, just skip the day or see if you can rent/borrow a ride.

Good luck.

 

Thanks for your input. That's what I was looking for.

This is a relatively small community, and I believe our online reputations are important, so I need to protect min for a min. I wasn't going to be "that guy" and run it into the ground on-track regardless. Ultimately, my biggest risk was the loading and unloading and driving to an event only to run 1-2 laps. We did replace the fluid and it sounds much better now. I simply haven't tested it under track conditions. What I meant was the risk of spontaneous destruction is low - no greater than any other failure. The most likely outcome is that it gets progressively worse, and I park it long before it results on an on-track failure.

As for refunds:
"Registrations may be canceled and credits will be issued minus $25 for fixed administrative costs up until 3 weeks before the event. No credits will be given after that date. NO REFUNDS will be given. Fully registered spots in the event are for the paid participant only and are non-transferable! The week prior to the event NO CHANGES will be made to the registration list." The event is tomorrow. They start tech inspection in a few hours. I don't want to be that guy either.

I don't know any AP1 owners that track their cars; though, that is an excellent idea.