WT160

I was having some ring gear shifting problems on my Trek 7000, so I tried to take the bottom cover off of the Shimano STX shifter to see if I could lubricate it. The bottom cover has a small phillips screw and allen bolt. The allen bolt was a little stiff, but never came off completely. I can't get to tighten now, either. The whole mechanism is now loose. I seem to be missing something here. Any pointers?

Amt0571

If you can't tighten or loosen it, you probably have stripped the threads. Do you have pictures? They would make it easier to help you.

WT160

I thought I might have stripped it, but I went back and forth, and I thought it was okay.

dsbrantjr

It sounds like the bolt or its mating threads may have galled or otherwise jammed. I would suggest trying to get some penetrating oil (Kroil or PB Blaster) in there and get the bolt turning again so you can tighten it up again.

70sSanO

Try this. But to give you an idea of what you are looking at, here are some old LX shifters. The difference is that yours attach to the brake level from the bottom (allen bolt) and mine attach from the top (allen bolt). You don't have to take the cover off, although it is nice, to spray WD-40 in there and then lube with Tri-Flow. I have not had great success if the shifter is worn. If it is just dirty/gummy, it will help. The issue you will have if it doesn't work is trying to replace just the shifter.

John

WT160

I sprayed it. The bolts just spins, even when I pry and twist at the same time. I'm not sure how to get the top from the other side off.

I found some old stock replacements, but should I upgrade to something like Deore XT ST-M760 instead?

KCT1986

Assuming front (left unit), is the shifter set to smallest chainring position? The interface between the shifter, brake lever bracket and the window gear indicator unit on some of these shifter must align to mesh together. This is in the small ring position (front) and small cog (rear).

Another possibility is that a part between the shifter unit and the indicator slipped out of place and no longer aligning properly.

Andrew R Stewart 

IIRC this version of shifters have the center bolt threading into a Tee nut. The flange of that nut can slip out of it's fitting and thus spin, like a stripped bolt might. The bugger is that these can also have some sort of thread locker on the bolt and help make the loosening more challenging, especially if the nut is no longer held in place. One trick it to pull on the bolt while loosening it. Not easy to do with just the 4mm hex wrench but does work. This helps to seat the Tee nut and keep it from freely spinning. Andy

WT160

Yes, it's all askew, but I can't get the cover off to try and get all back together.

WT160

Ha! That makes sense. I have tried to pull on the bolt while turning, to no avail.

KCT1986

Here is the exploded view from Shimano.

Not sure if the attachment will load, so if not, try the Shimano web site directly. It is under Manual and Technical Documents.

70sSanO

So, can you remove the gear indicator to get access to the tee-plate?

John

WT160

I'll try.

WT160

I got it. I was able to grip the top nut with a needle nose pliers. The top nut spun in the housing, as the bolt was rusted. Now I need to put it all back together.

70sSanO

Use a good screwdriver that fits correctly, spray it with WD40 or penetrating oil, and take you time so you don't mess up that bolt (threads or head).

John

WT160

I got it together finally. Thanks for all the help.
It's too bad that I had to go through with all of that, but it happens. I see now that I could have sprayed lubricant through the side.
Years earlier that T nut wouldn't have spun in its housing, but the bolt and nut were rusted and the aluminum housing couldn't take the torque necessary to free the bolt.