bcubed

I recently garbage-picked a late 90's Trek 8000 MTB.

It seems that the problems that led to its decommisioning are: peeling paint, minor rear brake problem, and trouble with the rear shifter.

The nature of the problem: when shifting into a larger chain with the thumb, the shifting mechanism works only occasionally. When it doesn't, not only does it not move the rear derailleur, but it offers no resistance.

Without tearing it apart, it seems as if whatever mechanism "grabs" the shift cable has either rounded off or broken off from repeated use.

Are Shimano shifters user-servicible? Are the internal parts available to the consumer, or is there sufficent parts commonality that I could raid the parts bin for this?

Luke52

Not as big a problem as you may think.

Over time, the grease in the shifter gums up and becomes sticky, preventing the ratchets and whatnot from operating freely.

On the top of the shifter, you'll see 2 or 3 small screws. Remove these, and the top cover of the shifter should come off. Flush it out with a lube of some form (I've used both chain lube and a light spray grease from an aerosol can with success) while working the shift levers, and it should free it up nicely.

gerald_g 

I took mine completely apart today and re-assembled after cleaning and lubing all the wee parts. There are 20 or more per shifter. The biggest issue being the pawls do not rotate any more due to gummed up old grease. The procedure is not for the faint of heart with many small parts. I took lots of photos to help myself re-assemble. It can be done, but it is tricky indeed. WARNING - Tricky indeed!!

wrk101

Or you can just buy replacement shifters at Niagara or similar for $12. I use the Tourney shifters, come in both six speed and seven speed versions. $12 complete with cables and housings for the seven speed, six speed are $9.

I usually try to free them up the old shifters first, but I do not put a lot of effort into it. Then I just go with one of the Tourney replacements. I have used a couple of dozen of these Tourney shifters over the years, just used a six speed set yesterday.

https://www.niagaracycle.com/product_...ducts_id=15889

gerald_g 

FYI.

This is what the 7 speed looks like disassembled. The pawl in the red circle is the part that won't catch the cogs to shift. (Due to gummed up old grease)



Here's a shot of the front triple shifter. The pawls in the upper right corner, and the one attached to the "up" shifter (not visible in pic) are the main issues here.

gerald_g 

Here's a before and after.

noglider 

Nice work, gerald!

Though as wrk101 points out, it may not be worth it since you can get replacements really cheap.

bcubed

Thanks for the help! I took the bottom dust cover off and yes, it was the pawl not engaging...when I pressed the pawl inward slightly with a small screwdriver, it worked perfectly.

I'm thinking it might pay to try to clean + lube it in situ vs. disassembly.

gerald_g 

Ya I agree that spray cleaning may well make it work well for some time. I was tempted to give it a go, just spraying, but decided I wanted to be thorough. The pawl should be freed up with some spray cleaner followed with a light lube.

Thumpic

put both shifters in a jar of mineral spirits for a day or 2.....remove them...flush 'em with WD40.....let 'em dry.......

grease 'em.....unless something has broken, most will come back to life......

rydabent

luke is right.

Its mainly the small pawls that are lightly spring loaded. No need to totally disasemble. Take off bike and soak in solvent or kerosene over night. Re lube and check that the pawls mover really free. Cheap easy fix.

LarryMelman

gerald_g - Which shifter are you showing in your pictures? (What model?) It appears to have 2 levers?

One of our bikes started to act up. It has this Tx-30 7-speed shifter: https://www.amazon.com/Shimano-SL-TX3.../dp/B001NVAI7U (wrk101 mentioned these in post #4)

When you push the "+" button, it usually jumps from whatever gear it was in, all the way to 7. To me, it seemed like something was worn out internally. It seems to be all-plastic.

So I took the bike to the Performance where I bought it, knowing that their service is poor but hoping it was a simple fix. They acted like they had never seen a Tourney before (indeed, nothing on their floor had them), and they played with it for a few minutes and declared it shot, and that I'd have to buy new shifters. I asked about a warranty claim since the bike is only 18 months old and only has a few hundred miles of use, but the shop guy said it's normal wear and tear.

I went home and got on Shimano's web site, and saw that a) that Shimano does not make Tourney any more, Alivio is now the low-end and b) they have a 2-year warranty on everything (except 3-years on Dura Ace). I went back to Performance and showed this to the manager, and he agreed to replace the shifters at no charge with a 2-lever design (which may be Alivio, but I'm not sure). He'll be returning the old shifters to Shimano, so I can't try to take them apart myself. They didn't appear serviceable, but I didn't look very closely.

Bikewer

I've re-vitalized both MTB and road shifters with spray-'em-out with WD-40 technique. After the carrier for the WD-40 evaporates, I re-lube with some penetrating graphite lube I bought...Seems to work well.

bellweatherman

Fantastic restoration. A very clean shifter now.

Just wondering. After completely breaking the shifter down, part by part. And then reassembling it... Do you then squirt WD40 between all the plates? Or grease? Or nothing at all?