How To Know If You Have A Lsd.. - BMW Forum - BimmerWerkz.com
3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

 
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#1 (permalink) Old 10-08-2004, 01:18 AM
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Hey I was just curious to know how I would know if I had a Limited slip Differential. I didn't see anything in my manual about it and I'm not good enough to know by looking at my car. I do know that I have the sports package...not sure if the sports package came with the LSD. Also, what are the basic benefits of a LSD? Thanks
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#2 (permalink) Old 10-08-2004, 01:39 AM
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LSD is more commonly known as posi-traction. Basically, the system in the rear of car transfers the power to the none slipping wheel when a spinout occurs.

ever try to lay rubber with your car and only have one tire track behind your car? (thats an open differential and not LSD)

Stuck in snow and only one tire will spin?? (open differential)

The benefits of changing over to LSD are obvious. In addition the Differentials control the final drive ratio of the car. People here swap Differentials to find increased accelation (at the expense of higher speeds/better fuel enconomy) or you can change the diff in the opposite direction for higher top/better full economy @ the expense of acceleration.

THis is an extremely common (and cheap mod) on motorcycles to. I switched out my spockets on my bike for a huge improvement on the accelartion end, but at the expense of top end performance.... hell I don't need to go 160 anways

IF you are serious about modding your ride, then this should be added to do you to do list.

NL

Outside of laying rubber to find out what your differential is, you could probably take you VIN number to BMW and find out.

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#3 (permalink) Old 10-08-2004, 01:56 AM
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The LSD was an option for some cars I thought. I'm just wondering what to look for if I got under there and looked or what to look for when I'm driving to know if I had it or not.
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#4 (permalink) Old 10-08-2004, 02:14 AM
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Is there any VIN info web page that will decode our VINs?

I try to avoid "THE DEALER" as much as humanly possible...
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#5 (permalink) Old 10-08-2004, 02:28 AM
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Here is a decoder: VIN Decoder

It doesn't tell if you have a LSD or anything but it tells you some basic stuff. Yeah I try to stay away from the dealer as much as possible...come to think of it, I haven't ever been to the dealer. I have always just ordered my parts online and looked up DIYs. If anyone has a better decoder that goes more into depth don't hesistate to list it!
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#6 (permalink) Old 10-08-2004, 02:55 AM
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Remember, there are benefits to open diffs aswell, especially in cornering. An open diff allows one wheel to spin slower than the other when going around a turn. The effect is tighter corner control.

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#7 (permalink) Old 10-08-2004, 03:24 AM
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two ways to check.. one get under and check the diff, it might say something about it being lsd, secondly if you get the rear end up, turn one wheel, and if the other spins the same way , you have lsd, if it spins opposite, its not.. i think (depending on what yearand auto or manual) most 325's came with a 3.15 diff with a 25% lsd

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#8 (permalink) Old 10-08-2004, 05:18 AM
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What?

No one remembers the movie My Cousin Vinny?

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#9 (permalink) Old 10-08-2004, 09:37 AM
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Quote:
Originally posted by El Presidente@Oct 8 2004, 12:55 AM
Remember, there are benefits to open diffs aswell, especially in cornering. An open diff allows one wheel to spin slower than the other when going around a turn. The effect is tighter corner control.
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Not necessarily. A 1-way diff (like almost all OEM diffs) will completely "unlock" when decelerating, thereby allowing the wheels to turn independently. The only diffs that decrease low speed handling ability are 1.5-way and 2-way diffs. Those are recommended for drift.

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#10 (permalink) Old 10-08-2004, 04:29 PM
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Word to uiuc240, except with a 1-way when you need to accelerate when turning HARD, which will happen very often in parking lots, You'll notice unless you get a torque biasing diff. If you wanna drift or burnout, a quaife is not for you, they are a step up from open, but not quite good enough.

BTW: They will not change your final drive ratio unless your ring gear is different when you install it. So, this dosn't mean you have to change the final drive ratio to alter your top end\acceleration when you get one.


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#11 (permalink) Old 10-08-2004, 05:35 PM
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Quote:
Originally posted by NeverLeaned@Oct 8 2004, 12:39 AM
LSD is more commonly known as posi-traction. Basically, the system in the rear of car transfers the power to the none slipping wheel when a spinout occurs.
They function on the same point that one wheel spinning is bad. Other than that they are completely different. Positraction uses pins to lock both wheels together. A limited slip, gives limited slip to the inside wheel and transfers some power to the outside. This is what the 25 percent lockup means. A positraction rear end would be 100 percent lock up.

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#12 (permalink) Old 10-08-2004, 05:58 PM
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Not sure about ancient posi-traction...

But most diffs these days are either "Torsen type" in that they use planetary gears to distribute torque...or they are "clutch type" in which case they use a series of many clutch discs that rub together. They *usually* move together (in a straight line), but when the wheels turn at different speeds, they lock up. This will cause the wheels to again spin at the same speed.

UNLESS, you reach the break-away torque, in which case, the whole thing lets go, the wheels will spin at different speeds, and you're back to an "open" arrangement (this typically only happens when you make a REALLY slow U-turn). This is also why most clutch type diffs make loud clunking sounds around corners because they are *not* reaching the break-away limit (since they are setup to drift) and thereby forcing the inside wheel to spin at the same speed as the outside wheel.

Anyway, Quaife is AWESOME for anything but drift. I would absolutely love one $$$

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