That is the right place and yes they can be a pain to remove..
But more importantly you said NOISE!!
I think you are in for more that just 'how do I add fluid'...
Best grab the online manual and follow the directions on how to remove the rear axle and see what's going on..probably have the makings of a bearing failure.
You should deal with this before something grenades!!
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)