Originally Posted by
howsteepisit
One time when I had tis problem it was caused by the the shifter cable not being installed properly under the bottom bracket, so it did not slide properly and it would self shift. Check both the routing and the lubrication.
I've had this problem as well. The reason that it becomes apparent going up hills is that there is additional frame flex. Because the cable moves less freely, the RD moves instead with the flexing.