My 2012 M3W arrived with grease filled bevel box.
I replaced that with redline heavy gear oil after numerous times of filling running and draining to get almost all the black grease out.
The whine (must have straight cut gears in the bevel box) is really getting under my skin so am thinking of injecting some synthetic grease in there to hopefully quieten down that whine.
If it was filled with grease only, so a mixture of grease and heavy gear oil should not be an issue.
Anyone done this or has any opinions?
The gear set in the BB does NOT use straight cut gears. They are the same as any other automotive differential.
I would not recommend grease of any type. I believe that the very early M3W's had a gear oil of sorts, but with the additive it turned very dark and thick. Some of the guys had to flush it out with fuel oil several times to get it cleaned out.
The problem with grease is that it will develop voids and you can lose contact of the grease with the inner bearings etc.
I believe that I was the original recommender of the Redline Heavy Shock Oil for the BB. It has been used in many Harleys to calm down the straight cut trans gear noise in 5th gear and is highly recommended within the motorcycling community.
Some here did have a slight drop in noise with it, but I believe the consensus now is that if your BB is noisy, it will always be noisy. The NEW M3W's tend to quiet down after a few thousand miles or so, but others are quiet from the get go.
There has been some discussion on lapping of the ring and pinion gears in an effort to "smooth" the teeth to quiet down the BB. Short of a total replacement, the lapping may be your best bet at this time. Even with a new replacement, I believe it's still a hit or miss as to whether you end up with a quiet of noisy BB.
Good luck with your BB.
