Hi everyone,
I have a question about the ASD (hydraulic locking differential) which was optional on a number of 124/140/201 diesels. From the EPC and service manual info, it appears that the ASD diff acts as a normal limited-slip diff until the computer decides to apply hydraulic pressure to the external collars, then allowing 100% lockup. Normal LSD only gets to something like 20-40% lockup, I believe, depending on the tension of the thrust washer pack (adjusts with different thicknesses). Right now there are a number of different claims & speculation that aren't matching up well. I'd hate to buy a used ASD diff, expecting to get cheap LSD by swapping that in, only to discover it doesn't work...!
UPDATE (March 2009) : Yes, ASD has LSD active at all times, as described above. The LSD lockup is 35% when new, but this will decline over time as the clutch pack wears. After 100-150kmi, the lockup can be near zero. Replacing the clutch pack costs $300-$400 in parts, requires a few tools which most DIY'ers may not have in their toolbox, and lots of hours of work. BT, DT. But I did convert an ASD diff to LSD, and install it in my 1987 300D successfully. It's been working great for 2 years now.
Best regards,