XTR ST-M900 Shifter right

M900 Shifter Pod service
Time	2 hours max
Difficulty	8 / 10
Tools	Inbus key ? mm; 10mm nut or ; Adjustable spanner.; non freezing grease.
	v · d · e

How to service a right side XTR M900 shifter pod

Disassembly

So here we go with new lube and less dirt in your M900 trigger. Scared already?

First thing is to remove the lower cover. In my case its just 2 screws, no need for explanation. Except that there is a version with just one screw for the cover.

After that the main nut can be removed. Be careful, its a LEFTHANDED THREAD!

Please note, that in the picture the plate holding the spring to retract the thumb lever is mounted the wrong way. Seems someone took that trigger apart before I did. Also note, that the main shaft with its 6 grooves allows those plates to be slided on in two ways. And only one of those is right.

After that you can pull off the first lever, together with its spring and its (slide bushing) washer.

On the lever there is this small hook-like part that is supposed to move very easily. If you trigger had problems switching with the thumb lever slipping or not engaging this is the part that is causing it. The hook is held by a small snap ring. Slide the snap ring off to the side, take out the hook and clean the little axle and the hole. Use a freeze resistant grease before putting the hook back in place. And don't forget the little spring.

Taking off the second plate you get to see the "trigger finger lever assembly" - one slide bushing washer, another spring and the lever. Take them off.

And also that thin brass washer plate

Underneath that is the ratchet mechanism. This little bad boy is the most complicated to reassemble. So read carefully now, I warned you! :roll: There are tree parts that need to be marked before taking apart or it will be complicated to find the right position later on. Those three parts, I don't know their correct designation, I will call them "outer ring", "inner ring" and "main shaft with base". So. Be sure to mark the position of the inner ring to the main shaft. And the outer ring to the inner ring.

Then you can pull out the main shaft (spring: boing!)

and separate the inner from the outer ring and you're done disassembling.

... erm actually not. The inner ratchet ring can also be taken apart as seen in this picture I got from user FluffyChicken. Thanks for pointing out!

Reassembly

After cleaning all the parts (and oiling them again if you were using degreaser ;) ) take a closer look at the spring that came out between the base and the outer ring. It has one hook pointing sideways (that fits into the plastic part of the outer ring) and one pointing upwards (that goes into the little hole in the base of the main axle). If you look at that spring from above, the first mentioned hook pointing at 12:00 position, the second hook should be pointing at something between 8:00 and 9:00. Then the spring is ok. If it is pointing to anything "later" than 9, it has gone weak. One possible solution for that (besides take a new spring) is to shorten it a bit. Snip off 5mm and bend a new hook.

With the spring sorted, grease the base, the spring and the outer ring, fit the spring like so.

fiddle the other ends hook into that little hole like so and be sure not to use that second hole. It won't work because of the spring rubbing against that white plastic! Slide the base all the way up into the outer ring, then use your markings to put the inner ring onto the axle. If you for whatever reason have no marking :roll: you may want to take a closer look at the following pic.

This is how it should look like before you proceed to the next step. That one (not spring loaded) hook of the inner ring must be in line to the little cutout in the base. Dont' slide the inner ring completely in yet. Just as far as shown above. Because now you have to put the right amount of preload on the spring. It would be no fault to first mount what you have now assembled into the trigger housing and fasten it to the brake lever so it wont come apart again when you now try to tension it.

Now turn the outer ring clockwise for about 130° so the spring supported hook pointing out of the inner ring fits into the cutout of the last gear in the outer ring (is that even correct language??) and slide the inner ring in all the way. I put a marking on this photo so you get what I am talking about

The next steps are as easy as putting everything together as you took it apart, but obviously in reverse order. That spring that retracts the "trigger finger lever assembly" might put up a little fight. But at least for the other spring, I have a last "top tip". First hook one end of the spring onto the lever. Then fit that disk thingy while hooking the other end of the spring into position 1. Then refit the main nut (left handed thread...). Make sure there is just a tiny little bit of tension on that spring now, even in position 1. Else rebend it a bit. Also make sure all the parts are aligned correctly, nothing is tilted, none of the last springs coils is squished underneath the disk thingy. Then just pull the hook into position 2 to put tension on that lever.

Version Differences

There are two different versions of the right shifter pod. The described above has 2 screws in the bottom cover, the other version only has that one little screw and no centre screw. That version seems to be rather rare, as of all the sets that I had (I have 6 at the moment) only one is with no center screw.
The two versions are completely different. The inners and the outers are not interchangeable.