New O-ring installed. It was generously lubricated with petroleum jelly at installation. As well, the entire splined area on both sides of the O-ring was coated with petroluem jelly. As was the splines on the output shaft. The same expert who told me about the O-ring explained that it is very easy to cut this O-ring by careless installation of the pinion assembly. Hence the overuse of lube on my part. As well as GENTLY pushing the pinion assembly onto the output shaft. Here's hoping it worked!!!