My rear deraileur (sp?) shifter has been acting up for awhile. The 'pawls' inside usually won't catch when trying to downshift. However, if I fiddle with it, sometimes they'll start behaving again. I squirted in a shot of TriFlow. Didn't help. Have considered taking the thing apart on my bench. Anyone dug into one of these before?

I understand there are many small pieces inside the shifters that want to gain freedom when given the opportunity - so if you take a shifter apart you may have small parts everywhere!

My suggestion, before taking it apart, is to first remove the shifter cable so you can be sure it isn't gunked up with corrosion or other stuff. If the cable doesn't move very easily, replace it then see if you still have problems. Shifter cables, including Teflon-coated cables, are low cost (<$3) and fairly easy to change.

www.sheldonbrown.com has some good tips.

Ian

You can generally take the cover off without parts flying everywhere. The shifter's guts are held together with circlips.

My first suggestion was going to be Triflow as it seems to be the magic sauce to free up sticky Shimano shifters but I guess not in this case. I've heard WD40 will work too so that might be worth a try. Either way I'd pull off the cover to make sure you get the lube where it's needed. It sounds like the pawl that engages the gear is sticking.

The SIS mechanism probably needs to be cleaned up. Lots of small parts, honestly I've haven't fiddled around with shifters but try the cable swap first.

My only experience with Shimano is their road bike stuff - Ultegra, 105 and Tiagra. Altus/Tourney/Alivio is their low to mid-level MTB line.

Give this a whirl if you need a parts schematic:
http://techdocs.shimano.com/techdocs/index.jsp

thanks for the replies. I'll check the cables for sticking. Wouldn't hurt to lub it either. I'll report back what I find.

I've had the same issue with my Shimano rapid-fire index shifters (don't know if that's the same as what you have). Sometimes they'll "grab" the cable and sometimes they won't. I have successfully taken them apart and lubed them, but they've started sticking again. Next time, I will try dry lube and see if it lasts longer.

You don't want a dry lube, you want a thin wet lube.

Finally dug into it and figured it out. Using a bike stand, I clamped the bike upside down, removed both shifter covers and placed it in the sun so I could really see what was going on. The spring & pivot were gunked up just enough to prevent the pawl from engaging the shifter cog.

Using LPS #1, I directed the spray right where the problem was, let it sit for about 5 min. then blasted it clean with an air compressor. Then repeated. Cleaned the front shifter out while I was at it. Then lubricated all the moving joints, and cables.

Went for a ride. Nice....rear shifter worked fine. Nice to have all my gears back, especially on the hills and after laying off the Summer (just too hot). I'm paying for it now though getting back in shape.....