Rear derailliur shifting issues.. not typical
 

This isn't normal not adjusted.. Ultegra with sram 11-28 cassette.. brand new chain

I rode sunday with no issues.. came home, relubed the chain and went out today and it was ghost shifting all over the place. especially in the middle gears. Came home and started over.. took the cable off, checked the limits which was fine. put the cable back on and adjusted for the 11 to 12 shift and it will shift fine up to like 23 and it starts chattering and being harder to shift up. then on the way down it will double shift.

ideas? maybe i'll take a video and post it unless someone has something to try.

Sounds like a very typical cable needing a cleaning & lube.
Possibly a wire strand has broken and is binding.

It would do that mid cassette but not at the bottom? weird. i guess i'll go get a new cable tomorrow and give it a shot.

I would typically check: 1) Derailleur hanger alignment. Also, is the derailleur sitting flat on the hanger? 2) New cables? Check burrs as usual, but also check if the housing is sitting all the way in the ferrules. 3) Assuming you have the correct chain width and length, check for a bent or tight link. 4) Is the cassette seated properly? A friend of mine had the same problem and it turned out to be a spacer issue. Luck.

1. Why would it occur suddenly? The OP does not mention any incident that would bend a hanger. It is possible that a previously slightly bent hanger could contribute to whatever is the primary cause.
2. Best option would be related to the cables, either seating or possibly a new kink, foreign matter, etc. I don't necessarily think a new cable is necessary, and may not be sufficient. Need to check housing as well, would not hurt to blow some sompressed air or wd-40 through the housings.
3. Tight link would not ghost shift but rather would announce itself only every 2 crank revs or more.
4. Could be a cassette lockring coming loose, but a spacer would show itself from the beginning.

It was a wet start to the ride sunday so I will check to see if something got gunked up. but it was shifting properly until the end. So something happened while i was wiping down the frame afterward or putting it away. I did check the lockring and that is tight because that was one of my thoughts as well.

That info reinforces the cable possibility. What works OK when things are still wet may not do so well once the water evaporates. I could be wrong of course, but almost always suddenly occurring issues have some connection to what occurred just before the problem arose.

well new cable didn't fix it.. trimming the housing so they weren't "fuzzy" at the ends didn't fix it.. removed the cassette and remounted it.. nope..

You may need to slightly change your cable-length/tension procedure. The cable may be slightly too long (relative to the housing), causing the chain to not go inboard enough, especially as you go to larger cogs (downshift).

Just because it shifts between the two smallest cogs well, doesn't mean it will for the rest of the cassette. As the RD downshifts, imprecision amplifies. This is more true as the number of cogs increases, as the narrower spacing is less forgiving.

What I do is:

Set cable attachment and/or barrel adjuster so that I know the barrel will need to be turned CCW to make the 11T to 12T shift. While pedaling, I downshift then turn the barrel CCW JUST until it barely shifts (it may be a bit noisy). I do the same thing as I downshift one gear at a time: turning the barrel ONLY if it doesn't shift and only just until it does. This will fine-tune the cable length for all gears.

Shift through all gears in both directions. Make minor adjustments to the barrel to further fine-tune: CW if upshifts (to smaller cog) hesitate, CCW if downshifts hesitate.


That all said, I'd also look at the hanger to ensure it's straight. The RD's upper-pulley can be perfectly aligned with some of the cogs, but the bent hanger can make it impossible for it to line up with every cog.

ding ding. whoever voted for bent RD hanger is the winnahhh. was off by 1-2mm when he put the tool on it. good to go now.