It's a Shimano Deore LX derailleur. It was shifting ok until I changed the cable and started dinking with adjustments trying to make it shift better. For a while, it would not even shift, then, after watching many how-to videos and much trial, error and frustration, I got it shifting decently. I have never tried adjusting one of these things before so I'm not even sure what it was that made it start shifting ok again.
It shifts into the largest sprocket but if I'm not paying attention, and holding the lever in far for an extra bit, it will go up to that largest sprocket then slip right back down to the smaller one.
After all the time it took me to get it to this point, I'm hesitant to try anything in fear screwing it up again. It's workable now but I know it could shift better.
Any simple solutions?