Rear Axel Randomly Seized

This is an Axel:

This is an axle:

It's possibly galled - when fine aluminium threads are tightening in to another alloy part without grease, the material sticks to itself and chews up as if some of the alloy gets transferred to the other part which adds resistance to the thread. It can be tough to fix once its happened - something like freeze spray can help shrink the axle and get lubricant between the surfaces but you need to be careful because the threads can strip.

It can also happen on certain extra fine threads if the grease isn't thick enough - moly grease or anti seize has particles which create a kind of barrier between the parts which can't be squeezed out as easily. It's normally when you have alloy in to alloy or Ti in to Ti. Steel or mixed bolts don't do it as much (they can still seize other ways though!)

Funny enough had it happen on a pal's Session last week then my Elevator yesterday. Appears to be an issue with UDH. Guessing related to the axle and hangar/derailleur both being 7000 series alloys. Galling is in effect. Shop mech has been using Motorex never seize with good results. I opted for Teflon tape on the axle threads as that's what I had on hand. Grease is insufficient.

I too had the (steel) axle on my Raaw Madonna v3.2 randomly seize a few weeks back. It too was torqued to spec with park tools grease on the threads.

Edit: with UDH rear end.

I tried just about everything to get it off, but the only thing that worked in the end was hammering an oversized torx bit into the axle, then using a very long lever and a lot of force.

I messaged Raaw and they advised me to user Motorex bike grease moving forwards.

Maybe the fine pitch threads with the UDH? I have have had an axle seize until I had UDH. I was able to get mine out, had plenty of grease on it. I have used some antiseize since without issue.

I switched to this Finish Line waterproof "paste" several years back after having an alloy to alloy seizure on a rocker link.
No shop could break it free. No soaking. No heating.

So I took my Milwaukee impact driver (not an impact wrench), dropped a 6mm allen bit in it & just sat there with the trigger pulled.
It made it's little ratcheting sound & I think it was a good 2-3 minutes plus before the bolt finally spun out freely.  Maybe longer.

Every 30 seconds or so, I'd reverse direction for just an "ugga dugga" or 3 to get it to break loose.

Impact driver for running in deck screws isn't hitting that deadly 250-400lb striking force of an automotive impact.  I just used the principles of vibration & duration.

Couldn't help with the Session aside from ideas and moral support since they were out in UT, but I was able to free mine. My axle is broached on both ends for a 6mm hex so I took a breaker bar and 6mm bit on one side, long hex key on the other. I approached it like I approach removing ball joints at home: slow and firm pressure. Wrapped a ratchet strap around the pedal and the breaker bar and tightened it down to add a constant load then began pressing down on the other side. Took a bit but the UDH hangar's mount threads gave up the ghost before the axle threads did. Once those popped, the tension on the axle is released and it unthreads from the UDH bolt easily. Just glad it happened in house while swapping rotors. Saw a number of issues online about this happening where folx drilled it out, but that seems a case of last resort. Work smart, work slow. Panic/frustration makes things worse when you start to work in haste. Should it have come to that I would've drilled out the UDH bolt so if I wasn't square drilling in it'd cut into hangar rather than the frame. 

A professional mechanic, as in works for professional road teams, showed me to use both teflon tape and pipe dope on important threads like BB's. Pipe dope is that white paste that plumbers use on house pipes.

I had an axle not want to come out a while back.

I noticed something felt off in the back. I went to back the axle out and remove the wheel to investigate and nothing wanted to move. Luckily, I had accidentally left my "shop cut them too short on accident" extra handlebars in my car. Bike upside down; 6mm hex with a 740mm cheater handlebar; and slow, steady-but-pulsing pressure. Eventually it backed off just a little but not before bending the hex wrench. I'm always paranoid about that so I had inserted the wrench as far as I could on the wrench so it's still in service today...it's just twisted a bit right at the bend.

Got the axle out, pulled the wheel off, and the UDH just falls out. Apparently some threads somewhere got mashed in one spot which threw off the tolerances and mutilated the threads in another spot and made it all a nightmare. As soon as the mashing backed off and broke free everything just let go.

It makes me curious about those upgrade all-metal UDH mounts. The metal/plastic hybrid thing from Sram seems suspicious...but then again maybe that's part of building a little flex into the mount to deal with derailleur strikes, etc..

I encountered someone who accidentally tried to remove the axle from the derailleur side, as a result the threads got torn up pretty horribly. Be sure that you haven't done that, if you have retighten the drive side.

Sram love using Torx. Perhaps they should have used T55 for this to discourage mistakes.

I'm blanking right now and can't remember for sure, but UDH hanger threads are lefty loosey correct?

What could be happening is that the UDH hanger retention bolt isn't 100% tight when the axle is threaded in and tightened. In turn causing the hangar retention bolt to simultaneously tighten, which creates more binding and tension on the axle threads than intended? 

And thanks for the Axle Foley reference Robot.

Have you tried using something like PB Blaster on the threads?  

If it's truly ruined you can probably drill it out and kill the axle and UDH to save the frame and wheel.  

Yes this can happen.  You can end up in a point of no return with both the Axle and the UDH bolt/Transmission hanger where they are locked together.  You definitely have the axle 1 full turn loose prior to snugging udh/derailleur bolt, if one of them is already tight, and then you torque the other, an angle grinder and drill quickly becomes the tool of choice for removal.  

This is exactly what I figured happened for me.

I'm guessing the hanger wasn't all the way tight. Axle went in and took up all the space it was taking up but then kept spinning which tightened the hanger and pulled the hanger threads for the axle away from the axle stripping those bad boys out.

I imagine that some of the times I went off/on with the rear wheel, the hanger loosened at the same time. A bunch of times loosening a little bit backed it off enough that there was some movement available. Upon remounting the rear wheel it did its hanger-to-axle thread-destroying shimmy.

I check my UDH tightness more often now (and always do so when the rear axle is removed from the frame).

I find 35nm for the transmission derailleur bolt insufficient and will loosen over time fwiw.  Not quite as big of a deal with the UDH hanger, but still I think 40-42nm is more appropriate.  

Yep, been doing that to all BB's since the Trek bonded carbon frame days. Stops the inevitable creak on those early carbon jobs and stops seizing for those of us in northern climes who ride all winter. Also works great on track cogs and lockrings.

If you Ugga Dugga....video it.