[SimpleJ]

I just discovered an issue on my ride this afternoon. The thumb shifter for the rear derailleur has got some play in it. What I mean by that is that the shifter will rotate as far forward as it would while shifting, only there is no pressure (it is not pulling the cable). When I let it come back and try to shift it again, it will, no problems. Its almost like a pull-start engine with teeth missing from the sprocket. I checked the cable--no kinks, mud, jammed twigs in the der. or anything.

Does this sound familiar to anyone? I'm hoping its just a cable issue and not something internal in the shifter. The shifters are a couple of years old, and the cable is about 6 months old. Thanks.

 

[What&son]

sounds like frozen pawl

There is a little spring loaded pawl that engages with the teeths at the drum .That drum rolls up the cable as you push. If the little pawl pivot is dirty, or got a bit rusty, the spring will not have enough force to make it move in to catch the drum teeth. Open the cover and have a look, check if that´s the problem. If it´s so, spray some lube and try to bring "back to live" the pawl rotating it a bit with your fingers or a screwdriver.
The fact that it does not engage first and it does after some movements, is that the pawl gets a bit alive with the action.
If that is not the problem, it could be that the insides of the shifter have play.(due to a crash on the lever)That will make it hard to engage as the drum teeth are so small that any little play will make them miss the pawl.