Got a couple of test drives in this evening, and sure enough, it drives smooth as silk, just like new !!
(sure hope it lasts,,,
Looking back through the replies by jmp417 and Jim Salvo on the other thread, I certainly have to agree with both. I 100% believe that the part I took out is IDENTICAL in every way, and just as good as the new part I put in. But having the new part on hand, I sure wan't going to take any chances.
Anyway, I did wash out all the OEM grease with parts solvent, and repacked it with with very thick, high temp "disk brake grease." And just like others before me, I'll bet that is the whole secret.
I found that the technical service bulletin on the Impala Headquarters was totally helpful, and illustrated and described the procedure exactly. -including using pressure to force the new grease thoroughly into the splines. (I had to improvise my own plug)
T I M E W I L L T E L L