This is new... I rode to a course from my house, shifting several times en route. When I got there, I waited for a few people. Then, when we were about to ride, I discovered that my rear shifter had somehow become completely nonfunctional. This is a SRAM X9 3x10 drivetrain, I think from 2015. When I press the release lever, the first time it gives a little click, almost as though it is going to shift... but, alas, it is playing with my feelings. No shift! A second press does nothing. Similarly, the other lever seems like it might do something, but it's already in the largest cog, so there's nothing to do.

So, my questions...
1) Any ideas what might have happened?
2) If I can get another SRAM 10-speed rear shifter (GX, X7, X0, etc) while I sort this one out, can I expect them to play nicely with my X9 rear derailleur?

There was no impact, no crash, nothing even slightly out of sorts until suddenly it didn't work at all. I'm at a loss. I'm also wondering if I made a big mistake going with a SRAM groupset. My previous Shimano groupsets are still working after years of use. So far with SRAM, both brakes (DB5 front and rear) and the shifter have completely failed. I really don't want to have to pay a bike shop over and over just to have a working bike, and it seems like SRAM's warranties are only usable through an authorized dealer, and naturally, they want their cut.

Anyway, sorry, venting... I find this very annoying. Any thoughts on what might have gone wrong? Any reliable repair guides?

Cable may have loosened. Check the bolt that clamps the cable at the derailleur

Cable attachment is my first idea as well.

Sorry, I should have mentioned... With the cable completely detached from the derailleur, the behavior is exactly the same. When I press the takeup lever or the release lever, there is effectively no movement at all. If I pull on the cable by hand and press the release lever, nothing happens.

So when you shift to release the cable to shift to a higher gear you cannot pull anymore cable?

I'm not familiar with SRAM, but when this happens with a Shimano trigger, it is either the cable housing is gunked up and the derailleur spring is not strong enough to pull the cable, (but can usually be physically pulled by force), or the shifter is gunked up and needs to be flushed out with WD-40.

Since you can't physically pull the cable, and usually there is no click when the shifter is gunked up, it makes me wonder if the shifter is broken. If you can get to the internals you can see if the pawl is broken or gunked up.

John

Well, I got adventurous... I usually avoid the "more force is better" approach, but this time I decided to give it a shot. I got a little plastic sleeve and put it over the shift cable where it first meets the top tube of the frame, close-ish to the shifter. Then I clamped down with some pliers and gave it a decent tug. Nothing happened for a few attempts, but finally there was some give, the release lever released, and the takeup lever started working again. I went through several cycles of this and finally got all the expected clicks in both directions. I did that a few more times and then reassembled and tuned... now it's working again. I assume that either the cable was somehow catching or grimed up (which seems unlikely on a clean 3-month old bike) or it's haunted. Calling Dr. Venkman tomorrow. Thanks for the replies... they definitely sparked the idea.

You should replace the cable and clean out the housing. If there is something catching it will happen again. Congrats on getting it freed up!

John

I would replace the housing as well; it could be fraying internally and might be the cause of the hangup.

Thanks. I'm a little new to working directly with shifters, but that seems pretty straightforward. Just for my education, is it really advisable to attempt to clean and lube the internals of an MTB trigger-type shifter? On some road units it's relatively straightforward, but for MTB it seems like it would require opening the case and doing a lot of painstaking part cleaning. Of course, I might be missing some easy way to do it.

Opening the shifter housing is usually a matter of removing two or three small screws. It's not hard to do, or to put it all back together. Give it a try.

I've never taken one apart to that level.
Popping the cover off tends to be enough.
Usually, a generous hit of WD-40 or similar will free them up.
At worst, a dunking in the solvent of your choice seems to do the trick.

I've been using two 9-spd trigger shifters, an X9 and an X7, both for several years and thousands of miles, with no problems as described. I would guess housing/cable was the cause of the problem.

I'm with all the other suggestions.
Your comment that it's only 3 months old is a concern, but you don't know how long that shifter had been sitting on a shelf before you got your evil paws on it and some gunk may have solidified. A good flush out with WD40 is a good first step. With a bike that young, I'd talk to the shop you bought it from next.

If I've misunderstood and it's well out of warranty, look at the cables next. Pull the cable out and see if it's frayed. If it is, replace both the inner and outer. If not (ie, you can run your fingers along it without injury... but LOOK first), check the ends of the outers for crimping. Then check the whole cable for crimping. Inners and outers are cheap so new cables are probably a good idea but it's always nice to know what the problem was.

And as you found out, educated force is often a good thing, it's excessive force that does the damage, and that's a relative thing.