The teeth on the drive coupling had sheared off.

I wasn't expecting a package when the part arrived LESS THAN TWO DAYS AFTER I ORDERED IT! I had my own idea about how I was going to replace the old coupler, which involved rigging a clamp to hold the shaft etc.

I read the instructions that came with the part and couldn't believe how simple it was. The female threads on the coupler are aluminum (soft) and the threads on the driveshaft are steel(hard) so it can be simply pried off with a screwdriver. I love it when brute force is the right way to fix something. The new coupling screwed on with a left hand thread, no problem. I was somewhat disappointed that I didn't get to the day tinkering, but for the price of a movie I got a new blender.

Part Select exceeded my expectations.