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I have an M37 and M101, this is the M101 but the wheel hub appears to be exactly the same as the M37 so this should apply to both.

I started with the M101 trailer as I wanted to learn wheel hub maintenance but still be able to use the truck. Once I know how to do this correctly, I can move on to the truck hubs.

I got the hub removed, greased the bearings, and replaced the seal part with a new (old stock) one. The bearings have no blemishes or corrosion so they appear fine to me unless someone knows a way to tell if a bearing is worn other than that.

On reassembly, it isn’t going in as far as before, with a single thread showing previously and now 2. Picture attached of how it looks now. The TM really does not say, other than don’t tighten it, which it isn’t, the hub moves free and does not appear to wobble.

How many threads are acceptable to show on these wheel hubs? I suspect I am fine, but wanted to verify.

I don;'t know, but perhaps the trailer was built by a different company, and they had different tolerances. Replacing wheel bearings and such isn' something I would have been capable of when I restored my own truck. Hopefully someone else will be along to suggest an answer. Hal

Did you drive the races out, then reinstall? If so, they may have not been driven in far enough.

When torquing the big nut, I run them tight enough that I can feel a lot of drag, then loosen just enough to allow free rotation.

At that point, I lock them down and cover it up. The amount of threads never came into play for me.

PoW

I did not drive the races out since I didn't have the press to do this, and they appear to be unblemished. If I find a bad bearing/race set in other wheels Ill probably give that hub to a shop with a press. I did have to drive the inner bearing and oil seal out with pvc and rubber mallet, which took a bit of effort but not extreme. When reinstalling the replacement oil seal, I drove it just under the snap ring line and put in the snap ring, then tapped the bearing in with pvc and rubber mallet to get a seat on the snap ring.

Ill use the technique you describe, tighten then back off, to see if I can get this wheel bearing adjusting nut in further. I am using the amount of threads as a measurement, its only a couple millimeters further out than original which -may- not be a big deal. The cover plate goes on with no problem so maybe this is fine. I just am not sure how tight of tolerances are required for this. I assume the consequence of being too loose is wobble and bearing damage?

Greasing bearings is messy.

It is fun learning how things work, I have a much greater understanding of the wheel hub now that I have taken it apart. The actual wheel is held on by the set of three wheel bearing adjusting nuts/lock parts, which is apparent after disassembly.