Circa 2004 9 speed xt, backstory – started with a stretched chain, replaced that(dmr 9 speed) and found it tricky to get indexing perfect, chain was trying to climb out of gear and a bit of slipping so…replaced the cassette, Shimano M770, new jockey wheels and cable, dry oiled.

Gear changes are crisp and accurate but…this same drive train is usually nice and quiet, it’s like normal chain buzz but way louder, not quite Trrrrrrrrr but not far off, checked clearances of everything and the chain is not coming into contact with anything, tension looks fine, on the stand it sounds like the noise is coming from the jockey wheels but they have been switched out and the new ones are exactly the same, it’s not running over the pin, fiddled with the B screw with not much affect, hanger not visibly out of line.

Before I buy a new mech…have I missed something really stupid?

How are the chainrings looking?

How are the chainrings looking?

Big one is getting there but the middle looks good, small one looks like new, but….switching between them make no difference to the noise, doing this demonstrated something useful though, the noise is very noticeably coming from the rear mech.

I think it could longitudinal if that makes sense, could be my imagination but the chain links don’t look like they are meshing lengthwise, resulting in noise/vibration coming from where the chain cas to get round the smallest radius..bottom jocky wheel..is this possible? duff chain?

Check for stiff link (s) in chain ?

My guess would be that the chain is running the wrong side of the tab on the derailleur cage, located between the jockey wheels. Or is that what you mean by not running over the pin?

Check for stiff link (s) in chain ?

The noise/vibration is consistently er..consistent through the full revolution of the chain, but I checked anyway(it’s on the operating table) and..no stiffies.

Sooo annoying when you can’t find something that appears so obvious.

Sounds/feels like a mismatched component not meshing/just meshing/badly meshing.

I’d be rechecking my jocks….hope get there

Road tested and the new cassette is the biz, changes are clean as a whistle, noise is less noticeable but I can feel it through the cranks, feels deceptively like a bottom bracket bearing getting crunchy(replaced that bout a month ago so no..) I used a screw driver like a stethoscope and traced the main vibration to the bottom jockey wheel..which was fine, and new, and the old one that came off is now in and the same.

There are quite noticeable clicks and crunches under load through the cranks, perfectly rideable but feels horrible.

Jockey wheels in the right way? As in rotational?

i know you said drivetrain, but can i just check its not fitted to an old orange five?
(source of all known mtb noises)
🙂

Jockey wheels in the right way? As in rotational?

For a moment there….no they are on the right way round.

i know you said drivetrain, but can i just check its not fitted to an old orange five?
(source of all known mtb noises)

Old Stumpjumper so no pivot bits to creak.

Just road tested with a load of lithium grease on the cassette, more bearable/almost imperceptible, I’m thinking if that doesn’t quieten it, it will attract grit, turn into grinding paste and wear the damn thing smooth…new technique.