Does Shimano XTR RD-M9000 SGS 11-Speed Shadow+ MTB Rear Derailleur Long Cage work with 10speed XT shifter? I just bought a used bike with a broken 10 speed XT rear derailleur. Would a NEW Shimano XTR RD-M9000 SGS 11-Speed Shadow+ MTB Rear Derailleur Long Cage
( 182006158222 ) be compatible with 10 speed XT shifter &amp; 10 speed Shimano XTR 11-36t Titanium Cassette that I have?
I can say from experience this does not work well at all.

Although as mentioned above the chain does run through the shifting is dreadful. I tried it with a 10 speed shifter but gears would always have a spot where they would jump.  

Just get a 10 speed rear derailleur.  You will be glad you did.