I've been having some diff opening issues lately that would lead me to think the diff is worn out in a clutch-type. It only seems to open when the fluid is very cold or very warm and in tight corners or around the neighborhood in the morning. When the fluid is cold the opening is smooth and predictable, but yesterday I was doing some back roads autocross testing, and it started doing this lumpy open-close-open malarkey that worried me a little.


Is it possible that the Mobile1 75-90 that I'm using is the problem? It's ~12k miles old. I replaced it twice when I bought the car last fall, as the fluid that was in it was pretty gross, indicating a likely lack of maintenance in the car's previous life. Also, the rear end had been replaced before I bought the car and it has junk yard yellow paint pen all over it.


Other than the opening issues, the diff feels fine, and usually drives fine, and locks up hard. My gut says that the Mobile1 is the problem, and that it certainly is old enough to warrant replacing. Am I on the right track here, or is this an early indicator of a dead diff?

 

Very possibly a worn out clutch-style diff. But, for peace of mind check the front swaybar. There have been a number of examples where people were 100% certain their diff had failed but it turned out the front bar was broken or disconnected somehow.

Yeah, I know, you can't feel anything funny and would definitely know if a front bar was disconnected. They all said that too. Check anyway, it doesn't take long and might save you the cost of a diff... The S2000's handling doesn't change as dramatically as you'd expect without a front bar but you do get a metric $hitload of inside wheelspin.

I hope it is the front bar, that's much cheaper to fix!

 

my car was doing the same thing when i had a broken front sway bar mount.. on tight low speed corners it would seem like the diff was open and spin the inside tire.

 

I'm going to ask a really stupid question here and I know that you're knowledgeable about racing and cars....

So don't jump all over me....

What type of clutch diff do you have?
I didn't see any previous posts describing a non-OEM diff.

If still the factory Torsen, then I'm going to go with low traction and wheelspin as they don't really wear out.

If you do have a clutch diff, then maybe it's worn.

Either way, check the swaybar.

 

Worn out fluid of any mileage shouldn't cause the problems you're describing, let alone fluid with only 12k miles on it.

I'm with captain pants and CKit -- Occam's Razor suggests that the problem is front sway bar-related. It seems extremely unlikely that the previous owner found a clutch-type diff in a junkyard.

 

In fact the thinner, less CSt the fluid, the faster it locks according to torsen. So no way.

 

I'm 99% certain that I'm still on the stock torsen. Sorry for being unclear. I meant that it acts a little like a worn out clutch-type diff.

I have a Saner 1.25" front bar, and as much racket as the $3 endlinks make, it's nigh impossible that it's broken. In fact, the endlinks are SO noisy that I'd lean toward them clunking around and shocking the tires and being possibly responsible, except that the wheelspin is always on corner exit after the car has settled into the transition, which seems thoougky illogical...

 

It was the bushing mounts that failed on my swaybar. My endlinks were fine. Acted just like an open diff on corner exit.

 

When did you start noticing these diff issues relative to when you put the front Saner bar on?

 

^^ I agree ^^

I've had 3 separate occasions with front bar issues causing these symptoms (i.e. open diff due to horrible wheel lift):
Sanner Bar:
1st Issue: Broken U shaped mount
2nd Issue: Broken end link

Gendron Bar:
3rd Issue: Bar was sliding through the U shaped mounts hosing the bushings.... just needed to add spacers to keep it from shifting around.

Sooo... Especially with you having the stock diff, I would highly suggest looking that front bar over closely.

-Dave