Rear axle woes

[lukecp]

Well, my 12 bolt rear in my '72 C10 started howling pretty bad the other day. I was on the highway, and i noticed a whining noise coming from the rear of the truck. I drove the rest of the way home, parked the truck, and forgot about it. I drove it again, and it was still there. So i topped off the rear axle, and it was about half a quart of gear oil low (leaks through the pinion seal farily bad). It quieted it down a little bit, but the howling is still there.

I am really sure it is the rear axle. If i stick my head out the window, i can clearly hear it coming from the rear of the truck. The noise is there regradless of what speed the truck is going. If i put the truck in neutral and coast, it is still there. If i put the truck in a different gear, the noise has the same tone, although it is hard to hear it over the exhaust. It is also there on all road types (asphalt, concrete, gravel). It seems the worst when i am slowing down, but it is proably because i can then hear it over my loud exhaust.

So, any guesses on how long i can keep driving the truck before i need a new rear? This one has at least 200k miles on it, enought to wear out 2 350's and put 30k on another. I know it won't be too big of a deal to change over to a junkyard unit, but i really don't want my rear crapping out on me on a dark night. The truck is my only mode of transportaion, and i use it to drive home from college about every other weekend, so i need to keep driving it until at least Christmas time, when i will have the time to swap in another rear, or look for a cheap econobox to putt me around.