Differential Dilemma

[Lof8]

So I've been waiting for a 3.25 LSD to show up in the classifieds. It finally did and I paypaled a relatively new R3V seller. Bmwway shipped me a diff with the ID tag bolt loose and the tag missing. Here is my writeup for that whole deal:

http://www.r3vlimited.com/board/showthread.php?t=207337

At this point, I'm trying to determine if I in fact have a 3.25 LSD in my possession. So, I'm asking for some help to identify this pumpkin:



Can anyone with more experience identify this as an LSD? Can I count the teeth to get the ratio?

Also, feel free to throw in your opinion in the feedback thread if I should expect the ID tag to come with my diff purchase.
Thanks

[bernzpeed]

turn it where the axles attach to and see if it turns the same direction, then it is lsd. if it turns the opposite way, then no lsd.

[Lof8]

turn it where the axles attach to and see if it turns the same direction, then it is lsd. if it turns the opposite way, then no lsd.

I did a few tests with my known 3.73 LSD to get a baseline and will compare this one with those results. I just don't like that the tag was removed. Theres really no reason for that.

Anyway to identify the ratio with the diff out of the car?

[Wanganstyle]

Count the teeth on the ring gear, write the number down

Count the pinion gear teeth,
Write it down

Divide bigger number by smaller, that's your ratio.

Diff tag is only for Id purposes, they are lost on these vintage cars often.

Some very old and more modern cars don't have stamped metal tags at all, my z3 3.07 Torsen LSD did not have a metal tag, only a sticker w bar code that easily wears out.

3.25 is pretty old..... In the 90's it
Was changed to 3.23 and 3.25 was discontinued-

[Lof8]

Count the teeth on the ring gear, write the number down

Count the pinion gear teeth,
Write it down

Divide bigger number by smaller, that's your ratio.

Diff tag is only for Id purposes, they are lost on these vintage cars often.
-

The smaller gear is not in view to count the teeth. I have to disagree that the tags are lost often.

[shiboujin]

do 1 rotation of the axle and count the rotations of the drive shaft flange. Tada!

[SlapDash]

I've had four E30s, none had diff tags...

[shiboujin]

I've had 2 dozen diffs. 2 didn't have tags. :)

[Lof8]

do 1 rotation of the axle and count the rotations of the drive shaft flange. Tada!

genius! :D thanks

[LJ851]

do 1 rotation of the axle and count the rotations of the drive shaft flange. Tada!

Agreed . with an lsd its super easy , count the rotations .

[bernzpeed]

also there is an S on top of the diff casing

[Teaguer]

No dilemma really.

It IS a LSD diff.
For the ratio do as mentioned and turn the input shaft 1 full rotation, keep track of one of the outputs and it should rotate 3.35 revolutions for every 1 full rotation of the input.
Done deal.

[woodisgood]

rotate ten times and count...seems like it would be accurate.

[Jean]

Sometimes guys at the yards remove the diff tags on purpose, so that might be a reason. It does look like LSD, the pumpkin on non lsd units looks different. Count it....

[slammin.e28]

I like to go to the yards and harvest diff tags. I'm going to have a charm bracelet made out of them and give it to my next girlfriend as an anniversary present, from the heart, of course.