On our '03 Ram Dually for quite awhile there will be a squealing sound from usually the left rear, but occasionally the right. Did it at times in Alaska last summer and here in Yuma, AZ. Now, I haven't pulled the dualies off yet. Sometimes it may take an hour of travel for the noise or 2 minutes. I tap the brake and it quits immediately for any amount of time. The fluid in the master cylinder is good to go, the rear end fluid is level is good. No odor or smoking. It does seem that in warmer temperatures and higher speed the noise will be more prevalent. I'm thinking that the rear end fluid as it warms up may be pushing past the seals and getting on the rotors causing the squeal but am open to suggestions.

 

I have now become an expert is blowing apart the rear axle. I have done it now many times and learned a great deal. There is a problem with the factory brakes. The first is the factory calipers where the special coated pistons swell in their bore and bind. The binding causes the pads to drag, overheat and wear everything out prematurely. The back end cannot be disassembled without changing the inner grease seals and the axle flange gaskets. Be very careful when reassembling or seal damage will occur! Use anti-seize on everything when reassembling. lastly, if the emergency brake shoes or the emergency brake cable is adjusted too tightly, the brake shoes will drag and occasionally squeal.