Alright, got a brand new xt crankset with a new sram pc 991 chain. As soon as first tried to ride with the setup my chain slipped whenever I had a lot of torque on the pedals when I stood up. I talked to a few people and they said try changing the cassette. Got a brand new xt cassette and still the same thing. I went back to my 1 year old shimano hg 53 chain that is a few links shorter than it should be and I seemed to have no problem. The next ride I broke a link on the old shimano chain and just decided to buy a new shimano lx chain thinking that all shimano would be best. well the new shimano is on and....it's slipping! I had someone suggest that readjusting your rear derailuer can sometimes help. I did that and everything shifts perfectly both front and rear. Any suggestions?? I didn't have problems until the new crankset was installed. Is it possible that something could be wrong there? I consulted the crankset manual and it appears to be installed correctly. Can there still be something wrong with my rear deraileur even if it appears to be in-line and shifts with no problems? any advice would be appreciated. I also took it into the shop and had one mechanic suggest the freewheel but my rear hub is only 6 months old.