Final drive / driveshaft horror!

[Howard J]

Started the job I was least looking forward to this afternoon, the swingarm/gearbox gaitor is split and I knew I needed to do it sooner or later, just glad I did it sooner! I knew all wasn’t good as I lowered the final drive and water came out. I think I have got away with it and it seems to be surface rust, final drive seal seems to still be sealing with no leaks and the final drive oil has no water or contamination. Gearbox side of things was fine as the water has come in through the gaitor split and then drained down to the final drive, also checked and cleaned all splines and they seem good.

 

[RallyeGS]

I changed a front gaiter on a 2006 GS a few years ago. Thankfully it wasn’t that bad. Is that drive shaft rusted through?

 

[RallyeGS]

I hope you got that bike for a song?!

 

[Howard J]

I changed a front gaiter on a 2006 GS a few years ago. Thankfully it wasn’t that bad. Is that drive shaft rusted through?

No, just surface rust, 2nd pic is it cleaned up.

 

[Ian J Hartley]

You could try covering the drive shaft in grease and try to work it into all the gaps before refitting. The excess will get thrown off doing no harm, but a thin residue will remain to help protect against further rusting if you get condensation.

Interesting to know, that the current models have a drain/vent hole being retro fitted at the lowest point of the swinging arm. So moisture ingress appears to be a known problem.

 

[waggy]

I would also check to see if you have good movement in the UJ’s before fitting. I took mine to Mikeyboy who was able to replace them

 

[Pukmeister]

As waggy says, check all joints articulate smoothly with no notchiness or roughness. As they only move through a constant small arc during rotation, the joints tend to push grease away from the needle rollers and develop a notchy feel in one spot. Sadly as 'greased for life' with no grease nipples, the only fixes are to replace the entire shaft at hundreds of pounds, or get mikeyboy to fit new needle roller bearings.

The surfaced rusting is only superficial, the shaft is thick enough metal not to rot through: I would use a rust killer like jenolite or rustoleum, then spray with two coats of Frosts chassis black paint.

BMW don't paint the shafts, they seem to have a very thin surface coating. Yet more penny pinching.

Closely feel the paralever knuckle for side play in the needle roller and trunnion during reassembly along with the swingarm taper roller bearings. I replaced all on my hexhead due to wear and corrosion which caused excessive play you could feel by hand.