The 1999-2001 G.V. had the filler hole tapped in the wrong location. The fix happened mid 2002 and you can see where they had the blind plug, (cap) on the lower hole and the fill plug (threaded) above that. The TSB (unpublished technical bulletin) stated to pick up the front end 30 degrees and check the oil level... if it was low at that angle, then you needed to fill it up.
What happens is that people and quick lube places check the level on the lift and the oil (grease) pours out which makes them think it was overfilled. The rest is history...after running it awhile the bearings starve for oil and then you have a problem.
If your vehicle was a early 02 it could still have the original wrong filler location, check and see if you have the blind plug below the actual threaded filler plug. From the sound of it; the bearings are probably toast. You may want to change out the whole banjo with a later model 2002-2005 if you can locate one at a reasonable price.
I worked for American Suzuki Motor Corp in Brea for 17 years in the technical dept.