Then you didn't get ALL the old grease completely removed. Please note, ALL of it. The motor also needs to be disassembled, cleaned, and lubricated properly. You have to re-lubricate it in every area where it needs lubrication, properly, without taking any shortcuts. The changer must also be adjusted as necessary, to standards called for in the service manual. Don't be surprised too if you wind up needing a rebuild idler wheel also. This AT-6 uses a higher mass tonearm, the M 55 was happiest in a changer with a lower mass, higher compliance tonearm, with lower friction bearings, in changers in that era, this was a LAB 80, Dual 1009, Dual 1019, or ELAC/Miracord job, Also this is assuming you are using a Shure original stylus or a Jico equivalent. Many other generic manufacturers of lesser quality, will need more tracking force to track correctly. This is also assuming the arm is properly balanced, and tracking force is set correctly. There's a reason why I recommend conical styli in this changer, and medium to heavy tracking stylus options on the Shure mentioned. It's called 46 years of experience dealing with this class of Garrard record changers.