rear mech gone out of index?

I wonder if anybody else has experienced this? I bought a 2006 XT RD-M761 (normal rise) RM, off somebody on here as it happens, and fitted it to my new build. Indexing it on the smallest sprocket, as you do, it ran smoothly. Also in 8th. But in 7th it was hunting to go up to the 6th sprocket, and so on up the cassette until by the time the shifter was in 3rd the mech had the chain square onto the second sprocket, and in 2nd on the big sprocket, so the final click on the shifter was redundant. (Yes, it is a 9-speed shifter!)

I hadn't experienced this before, but I changed the chain and then the cassette just in case, but the problem didn't change. However when I fitted a different rear mech, the system ran properly with all combinations of chain and cassette. So I can only conclude that the shifter is working properly and is properly indexed, but the rm is out of index - moving across further than it should for each click.

Has anybody else had this? The mech appears to be straight, but can a mech get damaged and go out of index in this way?

yeah i think i have seen this before, the mech is usually twisted in someway, not the cage but the knuckle area

It is not a 10 speed shifter perchance?

Only time i had something like this was due to stretchy powercordz csble .... but you ruled out cabble.

The usual reason assuming that it is the right number of gears. Is that the mech hanger is bent. So it will gradually get more and more out with each shift. Either that or the mech it's self is slightly bent. The bend might be in a direction that it's not easy to see, and looks correct when it's in the smallest cog. But it is usually visible when you change to significantly larger ones.

this is Anthony we are talking about, all the normal/simple stuff will have been ruled out hence my suggestion after his description of the problem. also, he tried another mech and it was all fine so it suggests the mech is the issue itself.

over the years i spent in the trade i have seen most problems, some aren't always obvious, dodgy mechs are less likely but also less obvious.

Might be wear on the pins that move the main body of the mech, if the mech has being hit by something, it will probably be that the gear it is in that will have play in it

Usually from the bike being dropped RH side, inside of the house (by the missus) while she is reaching for the vacuum

Believe me, my bike gets mystery scratches from inside the house

:xmas-cool:

I found my rear mech did the same, it was a bit rear mech hanger bent and the bottom pulley on the rear mech causing mine to jump the middle gears

I had an identical problem on my tandem with an M750.
The jockey cage is rather thin and easily twisted. Tedious trial and error of dismantling the cage and twisting the cage around the top jockey cured it.

Besides any damage, the only thing I can think of you got the cable route wrong under the pinch bolt - it sounds like it is pulling in a linear fashion still. Shimano actually recommend setting up the indexing using the 2nd to last sprocket; presumably because this would not be affected by any settings on the high or low adjustment screws.