Think thats an each price mate.
The clicking rear axle sounds like you're driving over broken glass or gravel when driving at very low speed... this problem is mostly when reversing at low speed, often going up a slight hill or down (i.e. not flat), and while it does click, its a lot more of a creaking sound this.
i don't have any of that, mine is a very distinctive Click Click as i drive off, and also change gear, and its inline with the movment of the car as the weight shifts from front to back on power transfer during gear change. and normally only 2 clicks as the car rocks forward and then back during gear change.
Thats exactly what I get, 2 clicks when pulling off.
I've never heared it during gear changes though