option code 220
 

I was looking at the option codes in the warranty book for my car and found 220. Bruce Anderson's book lists 220 as "Locking differential". Is that aka limited slip? He also lists 221 as "Porsche locking differential" . What could the difference be?

Option code M220 is the ZF Limited Slip differential. I don't know what the difference is between that and the 221.

C2 ...

If you find a '12' stamped into the bottom rib of the 915, between the 'Type Code' and the serial number ... you have a late 915 with the optional ZF limited slip differential! They were only stamped such starting with late-83 or so 915's ... earlier models had no such stamping indicating the presence of a ZF.