Properly lubed splines should easily outlast the engine, they should outlast 2 engines. For splines to last 46,000 miles without grease is almost unheard of on the Vulcan 750, but not that uncommon on many other bikes. You must of been one of the few lucky ones that got their splines lubed at the factory. I waited until 12,000 miles on my bought new '93 to lube the splines, and found them dry, with some damage, though no rust. They had started to chew themselves up (IMO, they should be made of MUCH harder metal) I packed them with grease every 10,000 miles after that, and they survived past 80,000 miles. Keeping them lubed seemed to pretty much stop the wear/damage, they didn't look much worse the last time I lubed them than they did the first.
I have used that 3% wheel bearing grease, and it worked just fine. But, I always relubed them every 10,000 miles without fail. The moly paste should last a lot longer. I am still doing mine at 10,000 miles, even with Guard Dog 570 73% moly paste, but that's most likely overkill. I am actually planning on waiting until my rear tire wears out to do it again, which will be around 18,000 miles. I packed everything with GD 570 last time, used about $20 worth of it.
Though it is usually the rear splines that fail, I still believe the front splines (in the U joint and on the output shaft) should be lubed too. This is the hardest part, as you have very little working room. Some say these are not as important as the rear ones, but I believe anywhere they is movement there should be lubricant.
IMO, from experience with an old '85 Goldwing with nearly 100,000 miles on it, that still had perfect splines, I believe part of the problem, if not most of it, with the Vulcan 750 splines, lies with the design of the splines themselves. The GW had much larger shafts, with much beefier splines. They were a lot deeper and wider, both the high points and low points. Each spline was much thicker than on the Vulcan. The GW splines looked a lot like the input shaft on a car transmission, while the Vulcan splines are a lot flimsier looking. The GW splines also fit together fairly tightly, with noticeably less play than the ones on the Vulcan.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
Last edited by VN750Rider/Jerry; 03-12-2012 at 11:52 PM.