Final drive

[g.s.john]

Just changed the oil came out pitch black and smelling like cats piss no play on wheel no leaks replaced with 200 ml of Castrol syntrax 75-90.
Why does the oil go black as there is no combustion in the transmission?

 

[mikeyboy]

The black oil is caused by the wear on the case hardening on the bearings wearing,
Drop the fd down and check the pinion bearings for play.

 

[g.s.john]

FD is quiet no vibration felt whilst riding would that be sign?

 

[mikeyboy]

I don't think you will feel much vibration from the pinion as it would be fairly high frequency,more likely excessive backlash but the bikes have enough of that anyway ,
Drop the unit and have a feel for play,
Good excuse to check the prop lower u/j and grease the lower spline anyway

 

[g.s.john]

I had to drop the FD to change the oil lower UJ is ok but I'll have to drop it again to check the pinion do I need to check for end float as well?

 

[UturnTony]

I had to drop the FD to change the oil lower UJ is ok but I'll have to drop it again to check the pinion do I need to check for end float as well?

Just check for side to side movement. If any at all the FD is on notice.

 

[Bendy toy]

My bike showed 34K when I bought it. I dropped all oils ASAP. The FD stank horribly. After that I changed the oil every other engine oil change. But at 50K the wheel bearing failed. Having seen Patzx12 FD stripdown with its blown bearings so sent it off to Mike. He said all bearings were shot. I also needed a new UJ and the trunnion bearings were toast.
Not cheap but hopefully I'll get another 50K.

 

[Santa-2512]

+ 1 For Mike,

I had, I guess 5mm of side to side play in my rear FD and whirred like a goodun when i sent it off


Now its go no play and it's silent

 

[g.s.john]

Just dropped the FD again this morning no play everything tight so pleased with that at 46.5K I will keep an eye on it.
Changed the gearbox oil and went out for a fifty mile ride round all nice and smooth as a smooth thing.

 

[mikeyboy]

Just dropped the FD again this morning no play everything tight so pleased with that at 46.5K I will keep an eye on it.
Changed the gearbox oil and went out for a fifty mile ride round all nice and smooth as a smooth thing.

Good news!
Worth dropping the fd down every service if you can,
It's a good health check.
No play at wheel or pinion and clean oil its good to go

 

[Bendy toy]

Grease that trunnion bearing. It's needle rollers which don't cope well with rocking motions. Wipe out the old grease and pack solid with moly grease.
Never do that on rolling bearings (50% max for them) but fine for a suspension bearing.

 

[Miserable Git]

Could one of you kind gents inform me what the trunnion bearing is please? Hope this isn't one of those ' which oil ' questions.

 

[adventuredon]

oh, and its not 200ml...changed it a while ago to 180 ml or 175ml

 

[Pauly S]

i change my fd oil every service, the oil costs peanuts...

 

[Miserable Git]

So do I with 200ml but I still don't know what the 'trunnion bearing' is.

 

[Bounce]

i change my fd oil every service, the oil costs peanuts...

Sound advice


Sent from my iPhone using Tapatalk

 

[Pauly S]

So do I with 200ml but I still don't know what the 'trunnion bearing' is.

i havnt stripped my 8k 1200 fd yet btw, i assume its the bearings which are used at the arse end to facilitate the fd to move in an angular fashion when the suspension rises and falls keeping the fd level, make sense?

 

[Bendy toy]

The final drive is attached to the swing arm with needle roller bearings. The bottom one is the trunnion. BMW use very little grease so the bearing rollers rub that out of the way and run dry. Soon enough, the needles have a flat on one side and the bearing is loose. Packing it full with moly grease helps to reduce the problem. The swing arms have the same issue but at least the rear pivot bearings are cheap. The front ones are very NOT low cost.

You will need a heat gun to soften the thread lock.

BMW started with 220ml of oil in the FD. But leaks and hassle caused them to drop that to 180ml. If it lasts more than 30,000 miles they don't care, but less oil can't be good for the internal bearings. I use 200ml at oil changes. There have been no leaks due to over filling.

 

[mikeyboy]

oh, and its not 200ml...changed it a while ago to 180 ml or 175ml

Expect premature pinion bearing wear then.
180 is not enough in my opinion

 

[Miserable Git]

The final drive is attached to the swing arm with needle roller bearings. The bottom one is the trunnion. BMW use very little grease so the bearing rollers rub that out of the way and run dry. Soon enough, the needles have a flat on one side and the bearing is loose. Packing it full with moly grease helps to reduce the problem. The swing arms have the same issue but at least the rear pivot bearings are cheap. The front ones are very NOT low cost.

You will need a heat gun to soften the thread lock.

BMW started with 220ml of oil in the FD. But leaks and hassle caused them to drop that to 180ml. If it lasts more than 30,000 miles they don't care, but less oil can't be good for the internal bearings. I use 200ml at oil changes. There have been no leaks due to over filling.

Thanks for that Bendy Toy, I'll be doing the 42,000 mile service in another 2,000 miles and I'll check it out. May have left it too long but we'll find out soon enough.