Nasty knocking from transmission

[Ralph the mouth]

Need some help please, only had my 1994 1100 GS for 5 weeks but covered 2,500 miles when a nasty noise starts tonight from the drive/transmission area, on a process of elimination I cut the engine left it in netural (power on) and coasted down a long steep tarmac hill. The noise was coming from behind the engine around the drive/transmission shaft, there is also a knocking like someone is hitting the drive shaft with a small toffee hammer, and you can reallly feel it through the foot pegs particularly the right one, anyone got any ideas, oh I'm on 54,000 miles

 

[Noel]

Gearbox output bearing is my thought, without seeing it or dropping the shaft off I can't commit to it.

 

[Ralph the mouth]

Ah bearing,

That makes sense as its a clunk noise, should have put two and two togther but I also had a small but constant fluid leak that after about three days made its way under the exhaust and pepperd fluid on the off-side edge of the rear tyre, making right handders a bit more fun. I'd wash the GS down and it would be okay for another 3 or 4 days, thanks for thoughts. Guess I need a trip to the fix it please garage

 

[Steptoe]

Put it on the centre stand, and rotate the rear wheel -

can you feel any vibrations/courseness ?

where from ?

 

[Ralph the mouth]

Nasty noise

Thanks, I'm back at work now but will do exactly that first thing when I get home tonight. Had to take the car to work for the first time in weeks today, no fun at all

 

[Ralph the mouth]

Spinning the RR Wheel

spinning the RR wheel by hand there's no odd noise wobble grinding or indication of strange sounds from the beval drive, however (sounding like Sherlock Holmes) the noise coming from the Drive Shaft housing is a low sounding version of the 'nasty loud noise' that I had when riding home last night, now I'm even more confused (which ain't difficult)

 

[Steptoe]

Take the rear bevel off - and see if the shaft U/J's fall to bits as you remove it, also see if gear oil comes out of the shaft - if they're/it's all ok - you'll now looking at the gearbox -

 

[Ralph the mouth]

One New Drive Shaft later

Ah, thanks for the advice. Beyond my ability but the rather excellent ex-BMW mechanic has replaced the whole drive shaft (yes, bits falling off as you identified) and the oil leak was from a switch (not the most technical description) located in the gearbox area. Got both done and dusted and jobs a "good-en" Cleared 360 miles Saturday early hours of Sunday, with nothing leaking on to my rear wheel and no nasty knocking. Back to long hot sunny days of 100 mile round trip every day, again and again. RESULT!