I had the same problem. First it happened at 4500 rpm then 4000 and lower. Last friday was very lucky to get home (last 10km drived just on battery).
To take it out I was busy all Saturday, mostly scratching my head and thinking how to get to the bolts without removing driveaxle and Y-pipe.
It could be done with a lot of different extensions, good 1/2 socket and tonns of swearing!
In my case the brushes was so weared I never ever seen enything more messy in generators in my life (well, I'm still maybe too young). Friend of mine tried to take the alternator apart to clean the messy and bumpy rings on the lath and broke it (it is not desined for unassemblying at all!). So I got another one, but was forced to keep the voltage regulator of the old one, because those 3-pin terminals could be different (were in my case)!!
Tomorrow I will try to install it back and maybe will take some pictures.
Good luck.
