...before engaging the replacement of entire body, simply install the replacement cable coil bushing (white one). It is a VERY quick fix and u will realize a noticeable difference in shifting performance. Specifically the white coil bushing allows cable head to seat deeper in the bushing and keep cable end from rubbing against inner body, yielding less friction and better shift action. Even at 40-50K I doubt u need new internals. EM3
sorry but this is not really good advice. the problem you refer to would have been most evident when the shifter was brand new. suggest you look up and read @graeme's detailed explanation in the thread I referenced earlier.
There's sometimes a buggy.
How many drivers does a buggy have?
So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.http://www.youtube.com/watch?v=GekiIMh4ZkM