I am working on a LHT with 9sp bar end shifter and having trouble with the cable adjustment. New chain, new cassette, new Gore Ride On sealed cable. I get the adjustment good in the repair stand but then it skips in the smaller three cogs when it is ridden. Readjust, works good for a little while and then does the same thing again. I am going to remove the cable and make sure all the ends are seated and square. I have checked the derailleur hanger and it seems fine. any ideas?

How did you check the derailleur hanger?

I can eyeball a 7-speed but I need a gauge to align a 9-speed. It doesn't have to be very far out to make the shifting act up.

Check the adjuster on the downtube, be sure it's not screwing in as you ride. I've had this happen on more than one bike. Put a dab of paint on it for reference.

Did you "prestretch" the cable system?
Are the pulleys excessively worn?
Is the derailleur excessively worn?
Is the rear wheel seated properly?
Is the hanger <= 5mm of being aligned?
Is there excessive friction in that cable system?
Is the cassette loose on the freehub body?
Is the hanger loose?
Is the chain the correct one for the cassette?
Is the shifter correct for the chain/cassette?

I checked things out closer and the cable is turning the adjuster on the down tube. shelbyfv, how did you stop it from turning?

Try a little bee's wax.

I used some teflon plumbers tape. That helped, but I still have to readjust it every couple of months. I realize the shifting is getting funky and look down and find the mark on the adjuster has migrated so I just line it back up. Of course if you disconnect or replace the cable you have to start over with a fresh mark once you have it dialed in. Not an elegant solution, but it works.

Clean the threads with some sort of degreaser or denatured alcohol and use a dab of rubber cement on the threads. Works like a charm.