I don't know for sure that the manual trans cars use them, but it's simply a shock absorber for the driveline and a stick, having a more solid connection, I think would need one even more than the auto trans. I just checked the FastLane listing for an 87 190D and it lists flex disks front and rear without any caveat about "for automatic trans only" or anything like that, so I figure satyr's car probably uses them.

Gary