Mountain Biking - Shifting keeps going out

I upgraded to the XT Shadow from LX this winter. It has been nothing but a pain in my ass. I set it up, and it shifted great until I put a load on it. So I put an inline barrel adjuster on and that allowed me to adjust the tension. The problem is: I'll adjust it correctly, or so I think, and it will work wonderfully for about an hour or so, maybe more, then it will start to jump gears, usually to a higher gear, and make that sound that says the chain is rubbing in the cassette. I have no idea what can be causing this. Has anybody had this problem? Any solutions? Thanks

IDK, maybe a week screw or something. Try loctite?

Most likely the ferrule isn't fully on the end of the cable housing somewhere (if you don't press it on fully before installing it can be easy to leave a few millimeter gap). That would easily cause the problem you are describing. Turn the screw all the way in and readjust the cable tension manually, then shift through rapidly in the stand and keep doing so until it stops coming out of adjustment.

The ferrule has nothing to do with shifting. Alls it does is keep the cable from becoming frayed.
Have you checked the hanger alignment? possibly could be bent.

Hanger alignment wouldn't be that consistently inconsistent (wouldn't be fine for an hour before acting up.) I may have misspoke, I did not mean the ferrule at the end of the cable that is crimped on, I meant the plastic pieces at the end of the cable housings, having these not pressed on tightly enough will definitely cause the problem.

Check to make sure the cable clamp on the RD is not slipping. Sounds like you are getting more than just stretch in your shift cable. If that is not the problem, you may want to start from scratch again with the derailleur set up and adjustment. Not to insult your work, but there is a definite order of steps to follow.

Has anybody had this problem?

No...my Shadow is Primo.

Check to make sure the cable clamp on the RD is not slipping. Sounds like you are getting more than just stretch in your shift cable. If that is not the problem, you may want to start from scratch again with the derailleur set up and adjustment. Not to insult your work, but there is a definite order of steps to follow.

I KNOW I am setting it up correctly initially. Set the high and low screw adjustment. Cycle through gears adjusting the tension to get crisp, quick shifts. I just couldn't think of where the extra cable length could be coming from besides the screw on the derailleur. I will definitely go through and check the ferrules. Thanks a lot for all the great ideas.

IDK could it be a bad spot on your chain or cassettes also?

Yeah start at the shifter and work your way back. Make sure everything is seated right. It's gotta be something with the cables/housing.

Sheldon Brown always said if it's still not working after going through it over and over and over again, then your hanger is bent.

how do you go about checking the hanger? Does the derailleur need to be removed? I can't see any variance from where it should be. It probably wouldn't be able to be tuned correctly in the first place, right?

If you tuned it correctly and it worked for an hour or so then it wasn't a bent hanger (unless you bent it while riding it.) In order to check it you would need access to a derailleur alignment gauge, which your lbs should have. If you know what you are looking for you may even be able to see it by standing behind the bike and looking closely at the hanger, although that is something that took me a long time to be able to recognize. I do still stand by my first guess that it's the housing stops. Good luck!