Truck Repair: trans noise, meritor transmission, gear noise

Question
i have a 2007 freightliner century with a meritor transmission. when i am in 10th gear and pulling a load, a grinding type sound can be heard coming threw the gear shift stick. if i move the stick to the right the sound goes away. if i let it go the sound comes back. is this a sign or symptom of something? if so what can i do about it? 10th gear is my highest, and the heavier the load,the louder the noise.

Answer
The easier place to start would be check the ride height of the truck if its off it will cause what sounds like a grinding noise in the transmission. then I would check all my ujoints and slip yokes and carrier bearing to make sure none of those are bad. if that still doesn't solve it your looking at the transmission. could be excessive gear noise could be wear in the parts causing a shift fork to rub on the gear. But would check those other things first before getting into pulling the transmission.