We need more details on the clunk....
when does it happen? - pulling away? travelling in 2wd, travelling in 4wd? Going over bumps, steering hard left (or right), braking
what is it like (ie just one CLUNK or goes clunk,clunk,clunk as he drives)
Lots of grease in the freewheeling hubs tends to be a solution for the manual hubs on the older Suzukis, the Jimnys have vacuum hubs which are different.
Sounds to me like they are trying it on, it looks like they randomly changed things to diagnose the problem.
Give us more detail :)
Martin