LSD????

Need technical Q/A then you're in the right place

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eun
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Post Sun Jan 29, 2006 3:35 pm

hello

ive heard everyone talking about lsd's etc but i dont get everything about them.

when people say big case,small case, what are the different ratios for
different cars, and what ratios effect top end/acceleration.

and another one what is lock uo 25% 70% etc what does this
do? :?

i want an lsd so bad but just like to know a bit before i try and buy. winkeye

if anyone has one for a 325 let me know by pm and il get back to you cheers eun :D
kam-325i
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Post Sun Jan 29, 2006 4:47 pm

LSD come in different ratios.

Low ratios = higher top speed, Loss of acceleration.
High ratios = Lower top speed, better acceleration.

Normal ratio for a 325i would be a 3.63 or 3.72.

Lock reffers to the amount of tourqe needed to engage the clutch packs in the LSD. All E30 LSD's have a 25% lock up. When one driving wheel loose's traction and starts to spin, the LSD part kicks in and transfers power the the wheel with the grip. If you had one wheel on tarmac, one in mud, the wheel in the mud would spin and you would be stuck, With an LSD fitted, the spinning of the wheel of the wheel in mud would cause the clutch pack to lock up and transferr power to the wheel on the tarmac.

Big case is said to be more stronger built than the small case.
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Cabrio
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Post Sun Jan 29, 2006 4:59 pm

Hi

What were you hoping to do once you got the lsd...is it for normal road use or a motorsport use as will affect what you may go for

Also what budget do you have as do have contacts to get all E30 parts but most have waiting lists for LSDs

Good luck
E30Adam
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Post Sun Jan 29, 2006 5:13 pm

Not being funny here but why do you want one if you don't know what they do?
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eun
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Post Sun Jan 29, 2006 9:11 pm

kam-325i wrote:LSD come in different ratios.

Low ratios = higher top speed, Loss of acceleration.
High ratios = Lower top speed, better acceleration.

Normal ratio for a 325i would be a 3.63 or 3.72.

Lock reffers to the amount of tourqe needed to engage the clutch packs in the LSD. All E30 LSD's have a 25% lock up. When one driving wheel loose's traction and starts to spin, the LSD part kicks in and transfers power the the wheel with the grip. If you had one wheel on tarmac, one in mud, the wheel in the mud would spin and you would be stuck, With an LSD fitted, the spinning of the wheel of the wheel in mud would cause the clutch pack to lock up and transferr power to the wheel on the tarmac.

Big case is said to be more stronger built than the small case.
cheers kam
helpful info there

i knew they had different ratios just dint know which ones were better for acceleration etc. and what ratios where better as i keep hearing 3.91 a lot :wink:
eun
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Post Sun Jan 29, 2006 9:16 pm

E30Adam wrote:Not being funny here but why do you want one if you don't know what they do?
sorry i think its came across wrong :mad:

i know what they do...i just dont know the terminology for them

i dont know what the best ratio is for acceleration or top speed
and i dont understand what the difference is between 25% lock
up and 75% lock up, or big case/small case

and seeing as this is an e30 forum i thought someone might be able to advise me in the right direction :wink:
eun
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Post Sun Jan 29, 2006 9:38 pm

cabrio wrote:Hi

What were you hoping to do once you got the lsd...is it for normal road use or a motorsport use as will affect what you may go for

Also what budget do you have as do have contacts to get all E30 parts but most have waiting lists for LSDs

Good luck
hi cabrio

just for road use mate......well for a bit of added fun really winkeye
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Post Sun Jan 29, 2006 10:04 pm

large case diff's are bigger and stronger and take alot more abuse than a small case.

Easiest way to tell is large case has 8 bolts on the back plate and small 6 i think

large case fitted to 325's and M3's

small 316,318,318iS and 320's

HTH

U don't want a diff with a lock up percentage more than the standard 25% anymore and the car will be really lairy in the wet. If u want that then just weld up a standard diff, u will be going sideways everywhere whether u like it or not lol
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Post Sun Jan 29, 2006 10:06 pm

Simon13 wrote: U don't want a diff with a lock up percentage more than the standard 25% anymore and the car will be really lairy in the wet. If u want that then just weld up a standard diff, u will be going sideways everywhere whether u like it or not lol
scrubs the shit out of your tires too, but i'm going to do it!!
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Post Sun Jan 29, 2006 10:12 pm

yeah when parking especially they jump/skip round wierd on full lock!
eun
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Post Sun Jan 29, 2006 10:42 pm

Simon13 wrote:large case diff's are bigger and stronger and take alot more abuse than a small case.

Easiest way to tell is large case has 8 bolts on the back plate and small 6 i think

large case fitted to 325's and M3's

small 316,318,318iS and 320's

HTH

U don't want a diff with a lock up percentage more than the standard 25% anymore and the car will be really lairy in the wet. If u want that then just weld up a standard diff, u will be going sideways everywhere whether u like it or not lol
cheers si :wink:

so can you fit a small case to a 325i if that was all i could find? :?
and is it not dangerous doing this.....whats the difference
between an lsd an a welded diff.....does a welded one just produce
more lock up?

i would do this but you make it sound really bad for sliding out?
would it be best to do this in summer if i decided to? winkeye
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Post Sun Jan 29, 2006 10:47 pm

A welded diff will not allow the wheels to turn at differnet rates when going around a corner...

The rears will try to push the car in a straight line, fighting the turning of the front wheels....
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Brianmoooore
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Post Sun Jan 29, 2006 11:14 pm

Strictly speaking, the diff fitted to E30 325s is medium case. There is a larger case diff fitted to big engined 5 series etc., which will not fit the E30 at all.
beem
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Post Mon Jan 30, 2006 12:44 pm

Brianmoooore wrote:Strictly speaking, the diff fitted to E30 325s is medium case. There is a larger case diff fitted to big engined 5 series etc., which will not fit the E30 at all.
Exactly right! 4 cylinder=small case, 6 cylinder=medium case, 8 cylinder v8's=large case.
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Post Mon Jan 30, 2006 3:16 pm

Ok if you intend it for road use and fun take it you want one as cheaply as poss.. and unlikely to get a good cheap one unless lucky

Whats your budget!!! Then people can try and find you one

No problem getting one just depends on budget etc
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Post Mon Jan 30, 2006 4:35 pm

Got mine back from a 40% rebuild yesterday! Great fun! :D

Now just got to get that leak sorted.
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eun
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Post Tue Jan 31, 2006 1:54 am

cabrio wrote:Ok if you intend it for road use and fun take it you want one as cheaply as poss.. and unlikely to get a good cheap one unless lucky

Whats your budget!!! Then people can try and find you one

No problem getting one just depends on budget etc
well i havent really got a budget at the mo just enquiring.

i have some 15inch bbs im gonna sell with tyres so if anyone wants
to strike up some sorta deal let me know via thread or pm winkeye