Shimano Derailleur Clutch Service

The derailleur serviced here is the 12-speed SLX I reviewed during the 2020 summer. A difference when it comes to the clutch mechanism is the lack of external adjustment for the SLX. I assume that it's the same with Deore as well. Note: Using the 5mm hex key, remove the derailleur from your bike before moving on with the procedure.

Turn the clutch off (lever position as shown). I could have spent more time on the initial clean. I continued to remove dirt where needed while taking the derailleur apart.

Behind this little cover is where the clutch magic happens. Three bolts hold it in place and they're removed with a 2mm hex key.

With the bolts removed the cover is ready to be taken off, revealing the inner workings of the clutch.

It's a relatively simple mechanism but boy, does it ever keep things quiet on the trail.

This side of the clutch is quite well-sealed thanks to a rubber gasket between the cap and the derailleur knuckle. Carefully remove this gasket from the groove it sits in.

With the gasket removed, it's time to carefully remove the 'chain stabilizer' – the round part – and the cam unit that sits to the left. Using a 2mm hex key, back off the cam screw a little to free up the parts.

With the clutch now removed, we get a better look at the plate axle (hollow piece that the chain stabilizer rested on). It's important not to get any grease on this part of the axle, or the clutch won't work.

The lower cage of the derailleur is under reasonable tension from a loaded spring and we need to remove it to access the 'plate axle.' To unwind it, start by removing the 'plate stopper pin' using a Phillips Head screwdriver. The pin sits on the lower cage just below the knuckle of the derailleur, where the clutch was just removed from.

With the pin removed, we can prepare to unwind the spring.

The lower cage with the pin removed.

The lower cage is stopped from automatically unwinding itself by the top of the derailleur. This is quite helpful when working on the derailleur with the stopper pin removed.

Carefully extend the upper cage of the derailleur while holding the lower stable to prevent getting caught from the spring unloading. Once the lower cage clears the upper section, it will begin to unwind, clockwise, and you will be left with this.

Now we can remove the plate axle. Using a 4mm hex key…

And a T27, undo the two sides. This disconnects the upper and lower halves of the derailleur.

With the plate axle removed we're left with two halves of a derailleur. The lower cage…

And the upper. It's a good time to clean the spring and the housing it's wound up in.

The plate axle. The shorter, smooth portion to the left is where the clutch rests and should be kept clean from grease. The right side is where a freshen-up is needed. This isn't looking too bad though.

All the parts ready to be cleaned and put back together.

Using a flathead screwdriver, carefully pry apart the tension clamp, a small amount, and slide out the roller.

With the two parts of the clutch apart, give it a clean.

Add some grease to the spring. This is to prevent corrosion as it sits wound inside the derailleur.

Carefully grease the backside of the plate axle (the section with the ribs). Remember not to get any grease on the smooth surface that the clutch sits on. If you do, carefully clean it.

Slide the little plastic spacer over the spring. Be careful to align the tab of the spacer with the same shape tab of the spring (opposite the hooked end of the spring).

The hooked end of the spring needs to be worked back into the hole above the silver plate on the cage. This is also where moisture is able to get to the internals at the rear of the clutch.

Gently twisting and angling the spring will see it slot into place quite easily. Here we see the hole that can allow water into this part of the derailleur.

Looking straight on at the spring resting in the slot on the back plate.

With a 4mm hex key in the end of the plate axle, position it into the upper half of the derailleur.

Carefully align and two halves, squeezing them together and begin threading the T27 and 4mm hex into each other (I need a third hand to capture that photo). Check alignment (image below) and with the two halves of the derailleur together, tighten the 4mm hex to 7.8–9.8 Nm.

While tightening, check that the tab of the plastic spacer is aligned to the slot in the main cage of the derailleur.

Now the upper and lower halves of the derailleur are back together, twisting the lower cage anti-clockwise will set it back into position, loading the spring and providing the proper tension.

Once rotated back around (roughly 270 degrees), relax the upper cage. The two halves will connect, preventing the tension from automatically being unwound.

Now we're left with something that better resembles a rear derailleur. From here we need to set the 'plate stopper pin' back in position.

The 'plate stopper pin' is screwed back into the hole below the knuckle at the top of the outer 'plate.'

Apply a little loctite to the pin. I was fresh out and had to come back to it once I picked up some more.

Then tighten to 1Nm using a regular #2 Phillips Head screwdriver. Check that the derailleur is tensioned correctly.

Apply a thin layer of lithium grease (Shimano recommends their internal hub grease) to the outside of the roller. Don't get any inside or the clutch won't work.

Using a flathead screwdriver to open the tension band, carefully slide it back over the roller. Wipe excess grease, making sure none gets inside the roller.

Now the cam unit and clutch can be set together. Make sure the long side of the tension band is at the top (as pictured).

Slide the cam unit over the tension band with the band's long side at the top. It's important that the cam lobe is in the off position.

The cam lobe sits in the yellow shape drawn here. It puts pressure on the band to clamp down on the roller, turning on the clutch. If the cam lobe is located on the wrong side (opposite where it is pictured here) the lever to turn the clutch on when the derailleur is back together won't work.

Check that the clutch lever is still in the off position. Carefully align the clutch and cam with the protrusions of the plate axle and cam lever.

Double check that the cam lobe remained in the correct position, as shown.

Make sure the clutch is resting in place, butted to the bottom of the axle.

Grab the cover gasket…

And carefully slot back into the recess. There's only one way it can properly sit.

With a 2mm hex key, tighten up the cam slightly. I found this to help hold the parts tighter while finishing than leaving it loose. For derailleurs like the SLX here, there's no access once the cover is on, so set the desired tension now. Check that the on/off lever is working properly.

Grab the cap and carefully place it back in position. Check that the gasket remains in place as the cap is placed.

With a 2mm hex key, tighten the bolts for the cap to 1–1.5Nm (light), checking that the gasket remains seated while doing so.

Job done. Check the derailleur again to make sure everything moves as it should and then mount it back on the bike.