What kind of diff?

[ciocc]

Hello,
I've found a diff for my car for a good price, but the problem is, I can't figure out what exactly is the diff ratio. The car the diff is coming of is an early model 318i. According to info found online, the ratio is either 4.10 or 3.91. Both of these are fine (mine is a 320i with a 4.10 diff). The vin of the donor is wbaak510909740391. Any idea what exactly the ratio might be? The seller broke off the id plate, but it's not very clear, I attach the image link below. Thank you for the help

http://imgur.com/a/1rEqq

[zaq123]

Hello,
I've found a diff for my car for a good price, but the problem is, I can't figure out what exactly is the diff ratio. The car the diff is coming of is an early model 318i. According to info found online, the ratio is either 4.10 or 3.91. Both of these are fine (mine is a 320i with a 4.10 diff). The vin of the donor is wbaak510909740391. Any idea what exactly the ratio might be? The seller broke off the id plate, but it's not very clear, I attach the image link below. Thank you for the help

http://imgur.com/a/1rEqq

that vin number is for 316i, prod. date - 1987-01-23. Can't help with the ratio, like you said 4.10 or 3.91

[ForcedFirebird]

Mark the diff on the output flange/case. Turn and count the input shaft turns until your marks line back up (one revolution).

[HerbE30]

Isn't there a tag on the diff? Or only for medium case?

[SkiFree]

Mark the diff on the output flange/case. Turn and count the input shaft turns until your marks line back up (one revolution).

Here's a visual for thus who are logically-impaired.

https://www.youtube.com/watch?v=FV3mU7WaFfA