Looks like the joint may be shot. They said when they replaced the RH boot the joint had seen better days - apparently one of the ball bearings dropped out on removal which shouldn't happen. Noticed a grinding noise on the drive home above 40 mph (window open of course). We've had a real cold snap here so lots of grit/salt on the roads. Strange that it wasn't making any noise before the boot change but seems like I was unlucky on this one.

How can I test whether this is the joint or possibly the bearing that's given up while the axle was being removed etc?