E36 318ti Diff Ratios

[Phil (Ari) 0]

I've just installed a LSD but am not sure of the ratio. Can I tell that from the Tag on the diff? It is: R 444V7022

[zero 1162]

4.44?   If its an lsd it should start with an "S"

[zero 1162]

http://www.bokchoys.com/differential/GearRatios.htm

[Phil (Ari) 0]

20 hours ago, zero said:

http://www.bokchoys.com/differential/GearRatios.htm

Thanks for your reply Nathan. I've checked (it is on axle stands at the moment) and both wheels rotate forward. On the dirt, both wheels drive, so I'm pretty sure it is a LSD, so it is a bit worrying that everything I read online also says it should start with an S. I also took the guess that the ratio is 4.44. Is there a way to check it properly though? I've rung the local BMW agent, they don't know how to check it. Perhaps BMW Germany?

[zero 1162]

8 hours ago, Phil (Ari) said:

Thanks for your reply Nathan. I've checked (it is on axle stands at the moment) and both wheels rotate forward. On the dirt, both wheels drive, so I'm pretty sure it is a LSD, so it is a bit worrying that everything I read online also says it should start with an S. I also took the guess that the ratio is 4.44. Is there a way to check it properly though? I've rung the local BMW agent, they don't know how to check it. Perhaps BMW Germany?

only way to know for sure is to take the diff cover off and have a look. 

It means replacing the oil but that should be done regularly on an lsd anyway.

It also means you can clean the insides much better than doing an oil change the conventional way.

[NZ00Z3 187]

This photo will help you identify which type of diff you have.

[B.M.W Ltd 950]

To get a close idea of what the ratio is, mark the axle and input/pinion shafts with twink to a reference point on the diff housing.  Rotate the pinion and count the turns and fraction of turns when you rotate the pinion to get the axle to rotate once. ie a 287:1 will be a fraction of just under 3 revolutions of the pinion to one revolution of the axle.

[alisterh 26]

I have seen diffs with R tags before from z3s. They seem to be small case clutch type lsd. Ratio will be 4.44.

[E30 325i Rag-Top 2957]

If you don't want to change the fluid and take the cover off then Glenn (B.M.W. Ltd)'s method above is spot on, not too hard a way to check your ratio and pretty reliable.

Might not tell you if it's definately an LSD as wheels will turn together for an open case diff in the same way if there is nothing binding in the diff or axles, but will definately give you an accurate measure of your ratio.

Tags on diffs often get changed or lost, so it's not always 100% that the tag reflects whats inside the diff housing. Seen some sneaky ones where "S" tags have been put on open case LSDs to sell them, never the other way around though.

[B.M.W Ltd 950]

It could also have a back yard lockie job done on it as well

[Phil (Ari) 0]

Thanks guys, I think I'll go with Alister's theory and assume it might be out of a Z3. It works 100%. I changed the oil when I bought it - bloody expensive stuff and only done a couple of auto crosses in it since. I'm converting it into a club rally car. Fitted new Bilsteins and springs to the rear yesterday. Sump guard today. Got new Bilsteins for the front too (all suspension bits from Suspension Tech in Akld) now waiting on some more parts to arrive. Once lockdown is finished, I'll get a roll cage, seats & belts - then just about good to go. Thanks again