Gear noise, rear end?
 

Are their any known problems with rear end gear, I haven't been reading lately to keep up on stuff. Truck has 50,000 miles on it and I have noitice now between 55-60 mph I have a gear noise, you can hear it on the gas and goes away off the gas, get over 60 and it goes away which seems strange. Also need to run about 15 miles to get it to warm up to where you can here it good.