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LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 12:40 pm
by anton
hi all
so im going to fit an lsd to my e30.
a friend advised to use the diff from e30 323i which is 3.46:1
he reckons this is the best.
3.91 being better but scarce...
any opinions?
I can get the 4.46:1 for R1200 which is equiv to 80gbp.
cheers
Anton
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 12:42 pm
by anton
sorry i meant 3.46:1
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 12:51 pm
by anton
the thing is, my current standard diff on the 325i has a leaking left output shaft seal. to replace the seal all the EXPENSIVE best money can buy diff oil needs to be replaced.... so i thought i might as well gofor a lsdiff.
3.46:1 should i do it?? or should i look for something else?
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 12:55 pm
by Speedtouch
3.46:1 will give you a nice high ratio for decent mpg and motorway cruising, at the expense of acceleration. The later Tech 2 325i Sport had 3.91:1 as standard, while most 6-cyl 320i/325i models here had 3.64:1.
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 9:43 pm
by jack148
how can you tell what kind of diff you've got??

Re: LSD FOR MY 325I e30, advice on ratio
Posted: Wed Jul 30, 2008 10:09 pm
by Speedtouch
Jack up the back end of the car, place on axle stands, then spin a wheel: if it's an LSD, the other wheel will rotate the SAME direction, if it's the normal open type diff, the other wheel spins in the OPPOSITE direction.
Ratio is usually indicated by a tag on the diff, eg S3,91 = LSD (S) 3.91:1, while 3,64 = Open type 3.64:1
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Thu Jul 31, 2008 7:41 am
by DHFiS
I have tried to show the tag in this picture. This one is maked S 410 so its a LSD with a 4.10 ratio

Re: LSD FOR MY 325I e30, advice on ratio
Posted: Thu Jul 31, 2008 9:57 am
by jack148
Cheers guys!
I have just aquired a spare rear axle, which included a diff. I have just had a look at it and have found that the tag as mentioned is rusted and shows no numbers.

I also tried the drive shart method, these turned in the same direction. So I think I might have a LSD.

There is a number on the casing(1210 421)dont know if that is relevant??
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Thu Jul 31, 2008 4:38 pm
by anton
mines says 40:11S0684 what would this mean, its on the tag?
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Fri Aug 01, 2008 12:33 am
by e30bmlover
mine says S3.64.... yer boi!!
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Fri Aug 01, 2008 6:04 pm
by fannyj
Hi Anton, 40.11 is a normal 3.64diff. I've recently acquired a 3.91 and it says 43.11 on the tag (43/11=3.91) or thereabouts..40/11=3.64 Hope that helps
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Fri Aug 01, 2008 6:09 pm
by fannyj
Another thing, i fitted the diff 3.91 diff lastweek. Definitely better in my opinion than the 3.64.When on the highway in 5th i am now lying at 3300rpm as opposed to 2950rpm with the 3.64,so it isn't too ridiculous.My motor is stock as well
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Fri Aug 01, 2008 6:36 pm
by Rav335uk
Fannyj you PM

Re: LSD FOR MY 325I e30, advice on ratio
Posted: Sun Aug 03, 2008 4:59 am
by Aiello
you can find out your ratio by marking where the axle turns with some white out or something and count how many times it turns around for you. so turn the shaft where the tailshaft attaches around 3.6 or 3.9 and 4.1 etc and the axle shaft should have turned once by then and lined up with the mark again, its a little un accurate but atleast you will ruffly know, besides if you really want rip the back cover off the diff since you should really clean it out first and attach a new cover gasket and see iff its a big open lump or you have some sexy clutch packs for a lsd in there. let me know how you went
Re: LSD FOR MY 325I e30, advice on ratio
Posted: Mon Aug 04, 2008 9:03 am
by anton
can anyone give me the part # of a diff gasket ?