jsdavis

I have a right side Shimano trigger shifter and it won't hold the 6th gear from the smallest (shifting towards lower/bigger gear) on the rear derailleur unless I apply upwards pressure with my thumb. If I just push the thumb lever, it will go into the gear but will release and go back down as soon as I let go. Is there a fix for this or does it entail replacing the shifter? So basically unless I apply upwards pressure on the shifter, I'm locked out of the 3 biggest gears on the back.

I also notice that on this shifter, for each set of 3 gears, if I shift one at a time I have to push the thumb lever further and further until I get to 3 at which point the lever resets. On some trigger shifters whether I push the thumb lever once or twice, the next shift I have to push the lever the same distance as that first shift. Is this by design or is that shifter just worn out?

Bill Kapaun

You might remove the bottom cover and see if the center screw is tight.

sk0tt

The grease in the shifter may have hardened up and causing something to stick, might just need a spray of WD40.

reptilezs

yea hose it down in solvent

Jeff Wills

Agreed- this is a common problem with older Shimano trigger shifters. Find an opening and squirt a bunch of spray lube inside. Work the shifter through the gears several times and it should improve.

bobotech

Yup, needs a flush with solvent and then lubed. Should shift perfectly after that is done. Yours are common symptoms.

Bill Kapaun

Normally, I'd say the solvent thing too, but the fact the lever must be held for some gears makes me feel there is more going on there.

bobotech

I'm thinking that there is dried up gunked up grease in a few of the catches that the pawls land in and that the pawls are slow to return causing erratic shifting.

Flying Merkel

Shimano shifters are lubed with white grease from the factory. It turns to gum after a few years, causing the ratchet mechanism to stick. Been able to get a few bikes cheap because of that. If you're lucky hosing it with solvent or WD-40 will free it up. Often they need a strip-down to clean out all the old grease.

PHT

The next step after a solvent flush is a solvent and brush scrub. You can do this with just the faceplate taken off the shifter- get in there with the longest bristles you can find and gently scrub. I always try just a flush first but if that doesnt work I am constantly surprised at how many shifters I can bring back from the dead without a full rebuild.