Open to lsd swap.

[Active16Bits]

Hey yall. I currently have a 325e with an open diff. I want to swap over to a lsd. I plan on getting one at my local pickapart since they're cheaper there than online or new.

My question is, how can you tell if the differential is an lsd without opening it up? I looked at mine and couldn't see anything stamped on it?

Oh and I have a "medium" case by the way.

[u3b3rg33k]

I want to say search. If you know how a limited slip diff works, you won't need to ask.



Anyways, if you turn one output shaft, the other will turn the same direction if it's an LSD, opposite direction if it's open/atb.

That still doesn't tell you the condition of the clutch pack. You'll also want to be careful of which ratio diff you end up with. An eta with a 4.10 diff would be stupid, imho.

[Active16Bits]

That's all I needed to know. Thank you.

[kronus]

There is a tag attached to one of the rear cover bolts. It should have the diff ratio and slip-ness. A 2.93 LSD will be labeled as S2.93, a 2.93 open will be just 2.93.

[kronus]

Also, for ratios, don't go higher than 3.46ish, anything taller than that would be inconvenient on the freeway.

[rThor432]

That still doesn't tell you the condition of the clutch pack.

This is a good point regarding used/junkyard diffs. It sucks to go through the effort to install one and then still only peel one wheel.

[Active16Bits]

Thanks for the useful info guys!

The yard has a week long warrenty so I'm going to pick one up while it's already under the knife.

[MR 325]

Also check E24 and E28 cars, not sure if you knew that...

[Active16Bits]

Didn't even think of that. I do remember seeing more e28's last time I went there. I couldn't find any information on the sizing of differentials in e28's though. I know theres "small" and "medium" ones in e30's.

Does this really make a difference? or is it the just the case size in relation to the ratio? Would I have to use different half shafts if I used another size differential? Excuse my ignorance, I've grown up on mostly fwd and solid axle rwd's.

[Active16Bits]

Also, for ratios, don't go higher than 3.46ish, anything taller than that would be inconvenient on the freeway.

How inconvenient? I know the eta has a tall 5th but my GTI is at 4,000rpm going 75mpg and that doesn't bother me.

[u3b3rg33k]

Well, the eta runs out of revs at 4800rpm, whereas your gti goes to at least 6000rpm.

The eta has the same .8 OD that all the G260s have.

[kronus]

How inconvenient? I know the eta has a tall 5th but my GTI is at 4,000rpm going 75mpg and that doesn't bother me.

Going to assume you meant mph. The problem is more of a mismatched torque curve - the eta's usable rpm range is like 2k - 4k, and a taller diff will have you running through that very quickly. A 3.73 puts you at around 4k at 80, which doesn't seem problematic until you realize that the eta's peak RPM is 5k.

[Wh33lhop]

Going to assume you meant mph. The problem is more of a mismatched torque curve - the eta's usable rpm range is like 2k - 4k, and a taller diff will have you running through that very quickly. A 3.73 puts you at around 4k at 80, which doesn't seem problematic until you realize that the eta's peak RPM is 5k.

With a G260, a 3.73 puts you at 3350 at 80. Even a 4.10 would put you at about 3700rpm at 80.

Personally although I'd prefer a taller top gear, I haven't found a problem with turning over 3200 or so on the highway with an M50, the lower gearing is too fun. Just sucks for your gas mileage in an eta, but a 3.73 would still get you some decent passing power until 90 or so.

[kronus]

With a G260, a 3.73 puts you at 3350 at 80. Even a 4.10 would put you at about 3700rpm at 80.

I was estimating up from a 2.93. Not good at math :|

[Active16Bits]

Thank you so much guys. I guess I'm going to hope I find a s3.73!