Argh! Ghost shifting is driving me crazy!

[Big Dan]

Sometimes is good to check the limit screws also.
Put it on the smallest cog and release the cable, check if it stays there or jumps.

[jamesau]

Go to shimano site and print out the service instructions:
https://si.shimano.com/#/en/search/S...7800&type=ROAD

Verify derailleur and hanger fixing bolts torqued adequately

Double check that the shift cable/fixing bolt/plate washer are all properly oriented and are not impeding derailleur range of motion.

Verify cable moves smoothly through all housing/bends including bottom bracket guide (do this by hand after loosening fixing bolt).

I prefer to set my derailleur limit stops without a chain on.

Try a different wheel

Verify proper installation of cassette with all spacers.

Use a Park DAG tool to verify hanger alignment

Stick with it and good luck.

[azrider]

Hmmmm.........if it were me, and I had done all of that I'd be checking the alignment of the hanger as others have mentioned

[eddief]

are the der cable heads seated properly in the shifter?

and i know this sounds dumb but someone i ride with (i swear not me) rode his bike a real long way with the chain not threaded through the rear derailleur correctly. he missed that little thingy right above the bottom pulley.

[weisan]

Originally Posted by texbike

Worst case scenario, I do have a 7800 shifter and rear derailleur that are known to be good that could be tested on the bike to see if they're the issue.

That's not a "worst case scenario" at all, sometimes that's exactly what it takes to regain your sanity!

I went through this scenario a few weeks ago, finally threw in the towel, took a set of shifters and deraileur AND chain AND cassette combo that I know is working perfectly on another bike (that I don't ride that often), transferred them over and voila! everything works as they should. I refused to spend another second trying to figure out why, life's too short, instead took the bike out immediately and rode like a madman!

[skouri1]

the only time i have had ghost shifting on that generation (ultegra 6600) is when a cable was shredding in the shifter, then it would get hung up and shift later... last time you changed the cables?

[palincss]

Originally Posted by texbike

-I installed the KMC chain the wrong way? Chains aren't unidirectional, are they?

Shimano Ultegra 10 speed chains definitely are unidirectional. I don't know about KMC.

[Matthew]

He changed the cables. And housing.

[josephr]

probably a combination of a weak RD spring and a weak shifter spring so neither can balance each other out and that's why you can't pinpoint the issue. I'd rebuild both, especially with that sort of mileage. Of course, I've been known to be wrong.

[OtayBW]

Originally Posted by texbike

Hi Dave. The chain rides up on the cog that it is on and causes clicking and popping as it stays in that gear. It sounds like it's out of adjustment, but I haven't been able to tune it out with the limit screws or tightening of the barrel adjusters.

Maybe I'm missing something here, but if the chain is riding up on a bigger cog (lower gear), then you'd want to loosen the barrel adjuster, no?

[oldpotatoe]

Originally Posted by muz

My money is on the jockey wheels being swapped after disassembly.

That's my guess also...since everything else is new.

[oldpotatoe]

Originally Posted by josephr

probably a combination of a weak RD spring and a weak shifter spring so neither can balance each other out and that's why you can't pinpoint the issue. I'd rebuild both, especially with that sort of mileage. Of course, I've been known to be wrong.

?? shimano..no rebuild, no new small parts..he's frustrated enough..

[charliedid]

Try this

https://www.youtube.com/watch?v=MniiwTLvo1c

[charliedid]

All joking aside: Assuming the cable is running free (as mentioned) I'd replace the jockey wheels and do not assume B-screw adj. is "fine" just because it was fine before.

[texbike]

Originally Posted by charliedid

Try this

https://www.youtube.com/watch?v=MniiwTLvo1c

Haha! That sounds like exactly what's needed!

Thanks for all of the suggestions everyone. We have company in town this weekend, so no time to mess with it until early next week. I'm going to work through the suggestions on here one at a time in an attempt to ID exactly what the issue was/is and will report back. Stay tuned...

Texbike