Tuning tightness on XT rear hub

Question

So, background... I just got done replacing the freehub body on my Deore XT FH-M8000 rear hub. I did this because the hub was "grabbing" when it should have been coasting such that the hub would pull on the chain and crank with noticeable force until it finally "let go" for a couple seconds, only to repeat this. I think the cause was that the 14mm inside bolt was loose, as it was very easy to loosen, contrary to most online resources which say it should require great force to remove. But, I replaced the freehub body out of caution, and I will inspect the other one and possibly have a spare.

But now that I've reassembled it, I'm having trouble tightening the axle properly. I figured the best thing to do is to tighten it until I couldn't feel any back-and-forth of the axle in the hub shell. That didn't quite do it, though, since once I locked it down in the frame I could wiggle the wheel side-to-side. I tightened the axle a little more and tried again... again, wiggles. Once I tightened it down to the point of getting no wiggle, I also found that there is noticeable drag in the wheel spinning.

So, a couple of questions...

1. Could I have done something wrong in reassembly? I have the Shimano dealer diagrams and manual, but there's a couple of things it doesn't address. For example, the seal over the freehub bearings are not even on the diagram, but I think I got it all together correctly.
2. Should the entire axle be greased? It looked like there would be space between the axle and the hub shell, so I didn't. I might have seen it wrong and introduced unnecessary friction. Possibly an error...
3. Does anything else come to mind that might have caused this?

Answer 1

The "art" of getting the cones (I am assuming your hub has cone bearings and not sealed bearings) adjusted to perfection is one of patience. If you tighten them until they do not have any play, once you clamp down the hub in the frame with the quick release, there is a tiny bit of compression in the axle that renders the bearing adjustment from "just right" to "too tight."

It is a little trial and error to get it just right. In my experience the bearing cone adjustment needs to be just a little loose, but just barely discernable. That tiny bit of play disappears once you clamp down the quick release which renders it perfect.

Having the right tools to do this adjustment makes it a bit easier. You need to have at least one cone wrench (a very thin wrench) for the wrench flats on the cone and another can use a standard wrench on a traditional wheel. For your hub, you need to use a 17 mm cone wrench and a 5 mm allen wrench. if you have a way to hold the other end of the axle to prevent it from spinning (I GENTLY use a vice or another wrench) it makes it easier to micro adjust the cones as it fixes in place one of the variables.

To answer your questions:

1. You may have assembled it incorrectly, so that could be a possibility. The dealer manual (which you said you already have) for the hub does address how the dust cover/seal goes in. I will point it out in an image below. The image also has the blow-up of all the parts in order of assembly.

2. The entire axle does not need to be greased. It is not a contact surface. I typically will apply a light "film" of grease on my axles, but more for inhibiting corrosion more than anything.

3. If if is correctly assembled, it should just need that trial and error approach of adjusting the cone on the non-drive side in small increments until it is "just right." If I have any issues getting it perfect, I would chose to error on just barely too loose than too tight, but I usually just persist until I nail it perfectly.

The following is from Page 25 of the Dealers Manual. I also added a link to the full manual below.

LINK to full Dealers Manual

Answer 2

I also have an XT rear hub (QR 6-bolt disc, M756), and I prefer to make the final adjustment with the wheel in the frame. This can be done with a pair of cone spanners. With it feeling very slightly slack on the bench, I need to loosen the QR, tweak the non-drive-side cone by a small fraction of a turn, retighten the QR, and test.

It's quite easy to overshoot and go too tight, including as you lock off when working in the confined space of the rear triangle, with disc brakes and in my case full mudguards. I still find it preferable to trying to get the tension right on the bench, accounting for the added compression of the QR.