[s-cars] New clutch, and rear diff limits

Emre Washburn yumyjager at gmail.com
Tue Oct 25 15:46:18 EDT 2005

What transmission are you running?

Also, this isn't the first V8 rear diff that I've heard of blowing on
a high HP car. It seems like it's ideal to run stock rear diff on a
high HP daily driven car. With the stock rear diff the tires spin if
there is too much power, with the V8, things go boom.

92 //S4
90 Cq
40 valves 'O plenty!

On 10/25/05, djdawson2 at aol.com <djdawson2 at aol.com> wrote:
> OK,
> So I was all excited... 12.4 at 113, and it seemed very limited by the clutch's inability to deal with a competitive launch.  So I called Javad (034efi) to discuss clutch options.  He had a unit built by Spec that he said was good to 600ft/lbs.  So I ordered away... intent on a more successful trip to the dragstrip before the season ended.
> I drove the car back from Boise to Denver on Friday night.  Got up Saturday, and started in.  About 6 hours later, I had my new Spec clutch in the car.  Everything's going fine.  Out for a test drive...
> I decided to see how this clutch would hook up under power.  I tried a moderate launch first... one that the Centerforce wouldn't hold.  Wow... this thing stuck like white on rice... impressive.  So now I'm all excited about the potential.  So I go for an aggressive launch... 6k rpm with a gentle engagement to build boost, and then let 'er go.  KABOOM!!  This was a sound I knew well from previous experience with other cars.
> The rear torsen diff had unloaded, to the extent that a hole was blown through the side of the case.  Fortunately, I still had my original diff... so I was able to swap that back in.
> So now I'm wondering... and scared.  Is this the limit of the drivetrain?  Are future trips to the strip just another blown diff waiting to happen?
> Anybody with experience... please share.  How do you launch?  What kind of abuse have you been able to put the drivetrain through without failure?
> Keep in mind, I'm not dumping the clutch.  I usually start at a higher rpm (6k'ish), let the clutch out enough to put a load on the engine so that it rapidly builds boost, and then gradually let it grab completely.  When done right, you get the feeling like you are in a slingshot... and there's nothing really sudden or abrupt about it.
> And yes... Mr. Pederson has repeatedly used the term "fuse."  Maybe my rear diff is now the fuse, instead of my clutch.  Hey, at least it wasn't the tranny.
> Dave
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