Something squeaks in my drivetrain while pedaling. It's louder in some gears compared to others. What usually would cause the squeaking noise?

A mouse, loose in your frame.

Utter lack of chain lube?

I lube it semi-regularly with Prolink. So I wouldn't say "utter" lack. Last time I lubed it was 1.5 weeks ago. I rode it about 200 miles since then.

Is there a way I can hook a mouse wheel to my chainline?

No one has any other ideas here?

I have had a similar problem. The noise on my bike comes from the rear derailleur. The only thing that has worked is use a lot of lube all over the derailleur. Lube in a pressurized can seems to work a little quicker than standard lube.

Close.

It's from the derailleur pulleys (which is why "lots of lube all over" seems to help).

A small shot of chain lube in the pulley bearings will help; taking them apart and cleaning & lubing is even better.

louder in some gears than others would tend to lead me to the chain (travels more circuits in lower gears). Could be lack of lube but some lubes don't play nice with water, believe it or not and squeak when contaminated - flush the chain with a good spray lube to see if that helps.

Thanks. I'll try these suggestions out tonight.

I had the same problem earlier today and I took apart my RD, chain, and cassette and cleaned everything and it was gone.