prairie 360 front diff ?

I have a Prairie 360. When I switch it from 4wheel to 2wheel it makes a small clunk sound. when it drops out out of 4 wheel.
The bikes seems to run fine in 2wheel drive and when in 4wheel drive, I don't actually know it's in 4wheel cuz I'm only
riding on the street but the 4x4 light comes on.
This is is my wife bike so I'm not real familiar with it.
Does this sound unusual or do you think I can still ride the bike
The front diff oil level is good and has been
changed recently.
Any feed back will be appreciated.

Thanx

you have to be at dead stop with it ,the clunk you hear is not good are you rolling when its going in?