Sorry as this is an oft repeated topic but this is doing my head in. I have a Zee mech (the longer caged variety) on a 1X10 drive train.

I replaced the chain and the jockey wheels last night as the old ones where worn. Now the biggest three cogs cause a complete racket (11-40 with expander). Shifting is crisp in all but the 40 tooth which has always been clunky. Chain line looks OK and this wasn’t an issue before. I have tried tightening the B adjuster but again this wasn’t an issue previously.

If I push the derailleur cage up towards the chain stay manually the noise goes away. I initially thought that meant my chain was too long so took another link out but it made no difference and I think its a bit tight now. Below is a picture from prior to removing the extra link in-case it helps.

id say thats too tight

i suspect its your lower limit screw (which is the top one) with worn jockeys they probably leant out a bit to compensate