Every Harley 4-speed Big Twin rider knows "The Leak": the ever-present oil leak from the main drive gear. Now Zodiac has "The Cure", a seal kit that will stop this oil leak! The stable and reliable Harley-Davidson 4-speed transmission has been built for half a century, but the oil leak has always been present. The reason is that Harley designed the main drive gear spacer without a seal. This state of the art hardened two piece stainless steel spacer features an additional Viton O-ring that permanently prevents oil coming out between the spacer and the main drive gear. It can be installed easily without disassembly of the transmission as it is located just behind the main shaft oil seal. Kits replace the OEM 35171-37 spacers from 1937 thru early 1977, OEM 35070-77 from late 1977 thru 1979, OEM 35070-80 from 1980 thru 1981 and 35079-82A from 1982 thru 1985. They include the spacer washer, spacer sleeve, Viton O-ring and detailed installation instructions. Order the Total Cure kit when you do not have the main drive seal.