Final Drive Oil Change and Magnetic Plug

[Eqyn Dad]

I changed the oil in my new final drive for the first time. The unit was replaced under warranty 800 miles ago.

The oil was dirty (dark) and the magnetic plug was covered in a gray paste like stuff - no apparent metal pieces or any feel of grit - just pasty.

In the past, I do not remember anything like this on the magnetic plug - but I never have done the first change on a new drive unit.

I would welcome comments - thank you.

[NoRRmad]

They All Do That.

Completely normal. Keep an eye out, though, for shiny shavings.

[wncbmw]

What NoRRmad said - with this addition. When I suspected FD failure and the fluid was drained, there was little doubt. It looked like a metallic soup! The previous change had some scattered flakes and I was told by the BMW techs not to worry. Some stuff on the plug is normal however.

[philbytx]

The goop on the plug is moly...they originally came from the factory with that in the FDssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss.

[Eqyn Dad]

Thanks for the info. Moly describes the paste exactly. I've decided to change the FD fluid with every oil change from now on just for the piece of mind.

Thanks again.

[philbytx]

Good idea. I do a 6k complete powertrain fluid change (engine,tranny and FD) on both my R and RT and, remember, to stick to 75w90 in the Final Drive. However, I use 75w140 in my tranny as it certainly smoothed out the gearchanges in both the R and the RT (different gearboxes), especially when hot.

[Sunbeemer]

That "paste" is the normal FD wear after 12000 miles. I saw it too, and am now changing at 6K mile intervals -and it's about half as muck!

[roadglide]

I used 75/140 Mobil one gear oil and change every other oil change.

[philbytx]

Roadglide, you may want to reconsider the use of 75w140 in your FD. 75w140 in the Tranny is fine, in fact, it is recommended by BMW. However, there's a whole school of thought that using heavier weight oils in the FD could contribute to the bearing failures. Not proven 100% but there are articles on the Internet and also in the BMWON on this issue.

[def38]

The grey matter is moly assembly lube used by the factory and some rebuilders. I add moly to both transmission and FD oils to reduce heat, friction, ease shifting and preserve bearings. Moly is an EP lubricant and friction modifier and is compatible with GL-5 and motor oils.

[def38]

What NoRRmad said - with this addition. When I suspected FD failure and the fluid was drained, there was little doubt. It looked like a metallic soup! The previous change had some scattered flakes and I was told by the BMW techs not to worry. Some stuff on the plug is normal however.

Any metal bits on the magnetic plug signifies the crown wheel bearing cage breaking up or brinelling in the races. This is generally understood to mean imminent crown wheel bearing failure. Most savvy BMW FD folks believe that the bearing preload was incorrectly set at time of assembly leading to subsequent bearing failure and a new seal and crown wheel bearing. Many riders perform a DIY repair.