2005 R1200GS Final Drive Service (GL5 Flush & Refill)

Begging forgiveness up front everyone. I'm a current and life long Airhead, but have been assigned the dubious task of maintaining a close friends 2005 R1200GS. I'm finding the learning curve a bit steep at times but enjoyable and quite manageable (with some help).

Already performed oil & filter change, air filter, transmission fluid change and am moving on to the final drive. I need to change fluid, service splines and replace the rear rubber boot (gaiter). The subject rear drive has only a single fluid drain plug. After some research I'm seeing some tutorials that require the hinge point to be unsecured and while the rear drive is hanging down the fluid to be emptied out the single plug port. Here's my question ...

Rather than disassembling the ABS sensor in-between the brake rotor and interior of the drive housing to re-fill with 180ml of GL5, why can't I simply pump new GL5 into the single port that the fluid was drained from? It's position seems to be more on a horizontal plane rather than the lower portion of the housing and I noticed to fluid exiting the port when removed. Dumb question? I'm not opposed to going through the ABS sensor but wanted to ask the question while waiting for parts arrival.

Appreciate my Airheads and their simplicity more than ever, but, am enjoying the experience with the GS.

Mike V.

I've never tried myself, but I do believe a small amount of the 180 ml of gear oil sits just above the drain. Otherwise, we all weirdos for following the official BMW REPRom for so long and filling through the speedo port

Edit - I see you said that you noticed no [sp] fluid exiting the drain before being lowered down - did you get out ~180ml of gear oil?

If you’re pushing fluid via syringe I’d be tempted after draining to swing the drag link up out of the way, raise the FD as far as it will go, and inject the lube. If it doesn’t work just swing it back down to drain and start over. But pulling the speedo sensor isn’t as onerous as cleaning & greasing a rusty driveshaft if you find one in that condition…

Please let us know how it goes…

Best,
DeVern

Thanks guys,

I have not drained and measured the existing fluid yet. Not sure where 180ml tops out yet at the port. By the condition of the bottom of the housing, it appears some weeping has been taking place for quite some time. The boot is in pretty poor shape with obvious cracking and not as supple as I would like. When I get access to the bike again I'll do some investigation and report back on how things work out.

30064 said:

Thanks guys,

I have not drained and measured the existing fluid yet. Not sure where 180ml tops out yet at the port. By the condition of the bottom of the housing, it appears some weeping has been taking place for quite some time. The boot is in pretty poor shape with obvious cracking and not as supple as I would like. When I get access to the bike again I'll do some investigation and report back on how things work out.

Click to expand...

Yeah, you’ll want to replace that boot and check the front one while you’re at it. Water penetration through the boot=rust on the driveshaft and splines. BMW uses a very sticky paste grease to help seal those boots from water intrusion where they clip in.

Best,
DeVern

Just to put a closing on my original thread ... I wanted to share what I've recently learned. Thanks again everyone for your help and responses.

While ordering parts from Rubber Chicken Racing Garage this afternoon, a couple of my questions were answered ...

Q: Why no drain and fill plugs on the final drive housing?
A: BMW originally considered this a non-maintenance item. That has since been amended along with revising the fill capacity from 220ml to 180ml.

Q: Will 180ml of fluid be below the drain plug?
A: No.

Q: Any special grease for the Boot lip contact points at the final drive housing when re-installing?
A: No, any good quality silicone or lithium grease.