Diff Ratio question

[mre30himself]

anyone know how i can tell what diff ratio i have.... My car is a 89 325 I i was told it came with lsd Thank you in advance

[daniel]

depends if it is an auto or 5-speed.

[E30_fiend]

99% chance its an open differential. If you have a 5 speed, you have a 3.73 open diff. If you have an auto, its a 4.10 open diff. The only way you have an LSD is if the previous owner changed it, unlikely, or the first owner got it from the dealer as an option when it was new







Taylor

[lennon]

its not that unlikely, these cars are 20 years old and changing diffs isnt unheard of. who knows the story. theres a little metal tag on the differential with the ratio stamped on it. if it says S3.73 or S4.10, the S means LSD. assuming the diff cover/tag is original to the diff.

[mre30himself]

where is the S located on the diff i did a vin look up on bimmer forums amd came up with this
209 LIMITED SLIP DIFFERENTIAL (25%) <<<??????? what is 25%

[E30SPDFRK]

If the diff isn't too rusty, there should be a large S on the bottom to signify LSD. If you don't see that, the ratio tag will be on one of the bolts holding the diff cover on. There will be a S preceding the ratio numbers.

Another was to tell is to jack one rear wheel off the ground and see if it spins freely. If not, it is a LSD.


The 25% is the lockup ratio of the diff.

[mre30himself]

the vin look up said lsd so im guessing it is but ill check just in case thank you for advice

[Jean]

%25 is the lock up ratio (standard % for stock lsd diffs)...

[Hallen]

99% chance its an open differential. If you have a 5 speed, you have a 3.73 open diff. If you have an auto, its a 4.10 open diff. The only way you have an LSD is if the previous owner changed it, unlikely, or the first owner got it from the dealer as an option when it was new


Taylor

It was an option for the 325i. Standard was open, but you could order one with the LSD. Sounds like that is the case on this car. (But checking the tag is the sure way to know... somebody could have switched in an open diff)