XTR 9sp crank with 10sp group?

You need to check to see if a 10 speed chain will fit the 9spd sprockets.

I'm running a xtr m970 crank w/ xt dyna 10 spd cassette and a slx 10 spd dyna rear d and shifter.
I even converted my crank to a 2x10 running a xtr 24t small ring and a 26t slx middle with a bash. shifts very good >
Just make sure to get a 10spd chain.

I am running a 9spd XT crank(set up as a 2x) w/ a XT Dyna r. derail, cass, chain and shifter. I think I swapped the front for a 10spd version, but am still running the front shifter that came w/ the 9spd pair. Zero problems, shifts great! I was on SRAM for years, but this new stuff really restores my confidence in Shimano.

It works no problem, I ran XTR 970 cranks with a 10 speed rear der, shifters, cassette, and chain- The only thing you have to do is match your front der to your front chain ring- the 10 speed FD's use the same cable pull but different geometry so will not work with a 9 speed crankset-

Check out this thread/Sticky for more in depth info.... http://forums.mtbr.com/showthread.php?t=646014

Agreed. My wife has been running that combo since the day I could first order it (last August-ish?). She swears the new 10-speed stuff shifts better, and it certainly shifts perfectly up front on the work stand with a 9-speed crank.

BTW, at the time of purchase, the Shimano tech rep said it would "absolutely not" work.