2004 2500 LD front axle noise

My 2004 2500LD has had a noise from the front differential of axle during highway speeds of 40-60 mph. It is a wurring noise that comes in and out every second or so. This can be heard over the radio at times. The front differential failed the input shaft bearing (lack of lube) and had to be replaced ... but noise remained after replacement.

Any ideas ?

There are many issues regarding lack of lube on K2500 GM axles. Right now GM has released a document stateing dealers are to replace all stock unit front axle oil with Synthetic. They have problems with the 9.25 inch axles (k25 & k35) email me and I will send you the document.