Gear Shifting Issues

alfa145

I wonder if anyone can shed any light on my problem.

Concerned parts: Shimano SLX M660 9 speed shifter, XT derailleur. Cable and outers replaced, well lubed, shifter stripped and lubed, but same issue.

Issue: Gears are indexed correctly, shift up and down fine when on the stand (up being smaller cog). When under light load - e.g. pedalling on the flat it will index down each gear correctly, but coming back up from say 8 to about 4 I find I have to do 2 changes on the shifter to get the chain to move up 1 cog. Or if I do one shift at a time I have to do 3 and then chain will jump to the correct indexed gear, but I cannot get anything in between. Gears 4-1 do shift correctly. I can't see any wear on the chain or cassette (both were new in October last year), and the problem was apparant before but has been getting gradually worse. Jockey wheels also replaced in December, but again - had no affect on this issue.

I think it is the shifter - is this likely to be the cause? What are failed shifter symptoms?

nicklouse

So. Issues are when pulling cable?

8 is a small size cog and 1 is the largest sized cog and the cable pulls the mech from 9 to 1 ?

alfa145

Correct - problem when pulling, but only between certain gears, usually between 8-4
(9 smallest, 1 largest)
9 to 8 works fine

nicklouse

Check the hanger is not bent . Bu it sounds like there is a cable issue.

The Rookie

B-screw adjusted correctly, I had this issue at one point after changing the cassette for a longer geared one and then realised the guide wheel was sitting 10mm off the largest gear.....

Simon

alfa145

The hanger looks OK - the 2 jockey wheels line up by the very unscientific method of eye sight, but I guess it doesn't take much to introduce quirky gear issues.

Good call on the B screw - I'll check tomorrow night

1mancity2

Take the chain off and check the hinges on the rear mech, I have slx and it sometimes gets really sticky and slow, good scrub and lube usually works but if not sit it in diesel.

w.jenkins

i have this problem too, really confusing me, am replacing cables but may end up changind rear mech as it is a little stiff

alfa145

I'm going to take a closer look tomorrow. I would rather identify the cause than start playing the parts lottery, but we'll see what I find when I can investigate it in the light properly. I will update tomorrow...

noppy

i had the same symptoms i ended up changing the cable outers and its done the job perfectly. Took a few gear changes to get the cable to settle in but it now flicks through the gears with ease rather than having a thumb wrestle.
i used jagwire outer if that makes any difference. :?

alfa145

An update - although it shifted fine with no chain on, and when on the stand I wasn't convinced it was right even when under load. The cables are as free as they can be, the derailleur is well cleaned and lubed and moves nice and freely with no resistance. When pulling lightly on the cable and shifting down it is OK, but when applying more resistance although it clicks the cable doesn't really seem to move enough.

So I thought it must be the shifter - I noticed quite a bit of play up and down in the down shifting lever, more so than on the front one so I took it apart. The nut was held in place by the tabs on the locking plate but it had spun round slightly, and the flat spring had popped between the lever and the washer - this is where the play came from. A bit of fiddling and a few swear words later I managed to get it all back in correctly and made sure the locking plate and nut are all in place correctly. Now the lever has no lateral movement at all and feels a lot 'tighter'. As it is rotating properly on the shaft and not wobbling about it I presume it is turning the ratchet properly. A noticeable improvement when shifting down just when pulling on the cable - proper movement between each click. I did all this off the bike so will fit it first thing and go for a blast, but fingers crossed :?