Limited Slip Differential - Alfa Romeo Bulletin Board & Forums

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post #1 of 4 (permalink) Old 05-23-2003, 02:30 PM Thread Starter
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Question Limited Slip Differential

Excerpt from AlfaCentro this month:
If your vehicle has a differential equipped with the original ratio, 4400 RPM in fifth gear should result in an indicated 88 mph. Your vehicle should have a 4:56 rear end ratio. The 4:56 in combination with the .79 ratio 5th results in an interesting phenomenon; doubling the indicated rpm in 5th gear will result in the actual mph - i.e. 3500 rpm=70mph, 2500 rpm= 50mph, etc. Your car came with a LSD equipped differential. The most easily identifiable difference between an LSD and non-LSD differential is the shape of the differential cover. The non-LSD unit is a symmetrical rectangle. The LSD equipped unit has a rectangular protrusion in the casting at the forward end of the cover.
Excellent information here - anybody who hasn't - VISIT THIS SITE!
Theoretically that means that at 6500RPM in 5th gear we could go 130MPH.
I immediately ran out to the garage in my socks and crawled under my car to see if it was LSD.
Now here's my question:
I was driving though a bit of dirt a few days back, and when I went to wash the backspray of dried mud a day later and noticed that the spray was only on one side - meaning only ONE wheel was spinning.
I thought that LSD meant that if one wheel starts to spin, then it will lock up and send both wheels spinning in a frenzy of tire melting excitement.
Anybody have any idea what the true nature of our LSD's are - compared with say a Chevy Positrak LSD, or say, my old BMW 535i?
Or - is my LSD busted?
Is there any way of increasing lock-up potential?

Jeff Nantais
1988 Alfa Romeo Spider is offline  
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post #2 of 4 (permalink) Old 05-23-2003, 03:03 PM
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Cool. My '74 has LSD.
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post #3 of 4 (permalink) Old 05-23-2003, 03:40 PM Thread Starter
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Did you just run out and crawl under your car?
Get some shoes on!

Jeff Nantais
1988 Alfa Romeo Spider is offline  
post #4 of 4 (permalink) Old 05-23-2003, 06:22 PM
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yes one can increase the lock-up by adding clutch plates. I have read that stock is something like 47% locked with one plate. adding a plate is like 74% locked. The % maybe off some, but you get the idea. I have not done this but have met people at the track who have. Some racer even weld up their diffs.100% lock-out. Thier cars hop skid and shake when making slow tight turns in the pits.
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