Shimano Deore LX Rear Derailleur, shifting glitches

[withiniswithout]

Update: Chain jumping and mashing the gears, seems to occur in gears 5, 6, and 7.
The mechanic at the bike shop said it was likely the barrel adjuster on the front derailleur, and to adjust it so gears 1 and 10 were both shifting with no problem. I thought, "It couldn't be that, something else is happening here." Well, there was some adjustment needed, and after tightening the cable a bit, it seems fine.
Lessons learned--

• I don't know jack sh*t about bike maintenance and I can be a bit paranoid.
• Start with the simplest fix, and go from there.
• Entry level components can last for many years and thousands of miles.
• If I had put on a new SLX or Shadow + derailleur and had the cables cleaned or replaced, it would have been fine but unnecessary. Bike repairs and upgrades are all pocket change compared to cars.

 

[Rás Cnoic]

If you haven't already give the entire drive train a good clean, degrease the chain and cassette check for chain wear. Replace the jockey wheels (Cheap to do) and did you get new cables back in June? Derailleurs do last a long time if looked after, unless they've taken a knock, they are very vulnerable to knocks. How many gears is it? A new Deore derailleur is not expensive, or the new Shimano Cues equivalent.

 

[withiniswithout]

If you haven't already give the entire drive train a good clean, degrease the chain and cassette check for chain wear. Replace the jockey wheels (Cheap to do) and did you get new cables back in June? Derailleurs do last a long time if looked after, unless they've taken a knock, they are very vulnerable to knocks. How many gears is it? A new Deore derailleur is not expensive, or the new Shimano Cues equivalent.

It is a 10 speed, with one gear in front. The chain and cassette are pretty clean. The cables were not replaced when the chain, rear cassette, and ring gear were replaced three months ago. The SLX RD-M675, XS short cage according to an internet search should be a compatible upgrade to the LX model. I would have been fine if the mechanic had recommended putting on a new derailleur and cleaning or replacing the cables, but he said it all looked good. I am conscientious about checking out things like chain jumping because I'm quite vulnerable if the bike breaks down and I rely on a good mechanic to keep things up to spec

 

[Rás Cnoic]

If you have the option of another bike shop or a friend who is local and bike knowledgeable it might be worth them checking the bike and getting some more advice. That original mechanic sounds a bit flippant. There can be cable stretch which can knock the gears out of sync. It's hard to be certain from afar, though it sounds like you checked things out fairly thoroughly.

 

[withiniswithout]

Thanks, I might look for another option. A friend has somebody he goes to that is good. The mechanic and the shop is close to the house and they are really good with many years of experience. But the communication and attention is often lacking. Part of this is cultural. I am an American in Italy, and I'm working with Italians. You get the feeling at times that they err on the side of saving money and getting by.

 

[stompandgo]

Skipping gears mid cassette is a symptom of a loose lockring. Pull the cassette off, clean everything, reassemble, and torque everything back down. If it's a HG cassette, pay close attention to the shift ramps in each cog.