Clicking From The Drive Train

[cammmy 1]

Hey Guys.

 

There is a really tight up hill left hander near my place. I notice that whenever i get any of the wheels spinning really good in my 4bie, there is a clicking noise coming from somewhere in the drive train. I assume it's the viscous diff that splits power between the front and rear axels. What I want to know though, is this a normal noise? Only ever happens when i'm losing traction.

 

Cheers