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Old 02-27-2013, 04:12 PM   #1
blacksparrow
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Question LIMITED SLIP BREAKAWAY TORQUE

Dealer checked the LSD in the 62k car I am looking at and the breakaway torque was at 50lbs, Within spec of 30-57lbs as stated by Steve Wiener in a previous thread here.

Does anyone know what end of the scale this is on? Assuming as it gets closer to the 57lbs it is closer to out of spec or maybe this makes no difference... not sure how it works.

Any thoughts?

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Old 02-27-2013, 08:07 PM   #2
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As the diff wears out, the torque would reduce.
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Old 02-27-2013, 10:58 PM   #3
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My diff was 'so' wore out that the shop thought it was not a LSD. When it was opened up, the insides were coated with black. The disks were so used up, some were smooth, no groves in the carbon disk material.

Bottom line, break away torque will get reduced as it wears out.

The shop (JB Racing in Tavaris, FL) worked with Guard Transmissions to get their internal parts that will work with the OEM carrier. Now I have the benefits of a Guard Trans and the cost savings of the OEM housing.

Win/win. Ican't wait to see how this feels on the street!!!!!
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Old 02-28-2013, 12:31 AM   #4
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Quote:
Originally Posted by Paul902 View Post
As the diff wears out, the torque would reduce.
Thanks, exactly what I wanted to know... I had the porsche dealer do breakaway as the car has more miles than most say that differential will be working. They say it works and that it is at 50ft lbs. Hopefully that will last a while and then...

Quote:
Originally Posted by mr_bock View Post
The shop (JB Racing in Tavaris, FL) worked with Guard Transmissions to get their internal parts that will work with the OEM carrier. Now I have the benefits of a Guard Trans and the cost savings of the OEM housing.

Win/win. Ican't wait to see how this feels on the street!!!!!
this would be the next step... it sounds amazing, let us all know you like it!

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Old 02-28-2013, 12:47 AM   #5
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Exclamation PIX

Also here are a few pix of the LSD after they did the breakaway test, they opened it up for me... looks like there are still some grooves left!
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Old 02-28-2013, 01:08 AM   #6
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Can you explain what was involved in the breakaway test? I.e. how done, tools involved, etc.
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Old 02-28-2013, 01:16 AM   #7
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Quote:
Originally Posted by TheOtherEric View Post
Can you explain what was involved in the breakaway test? I.e. how done, tools involved, etc.
I found this cited as the only real way to difinitivly test the LSD here on the forum... it was in one of Steve Wierner's threads.

They way i understand it is you test at the CV joint, not the axle. It is done with a special tool and a torque wrench.

The values he noted for 993 LSD were between, 30-57ft lbs torque is within spec... I just learned here, thanks to these gents, that it diminished with wear... so as the number gets smaller, the more wear.

I am no expert, just learning all this, so I hope I have not miss-spoken!

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Old 02-28-2013, 08:45 AM   #8
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This is a great pic of what makes the lsd work
Click the image to open in full size.

on the left 2 plain(external drive) and 2 friction disc(internal drive) stack
on the right asymmetric 25/65 ramps used in the street lsds

breakaway torque was usually low on these compared to older 911 setups, rather they relied on the asymmetric clamps to dynamically clamp the disc stack tighter for less slip.

25/65 means more clamping force on trailing throttle to help stabilize braking
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Old 02-28-2013, 11:18 AM   #9
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Great pix!!!
On my friction discs, two sides were practically totally smooth. Yours look very good.
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Old 02-28-2013, 11:18 AM
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