This just started about a month ago and it is driving me bat**** crazy. It is a medium pitched whine coming from the rear. It is a constant whine that changes with speed. It does not do it on curves or in parking lots. The truck has 161500 on it. Should I get a new rear end?

 

It could be a number of things unfortunately. An easy thing to check is the pinion bearings. Move the drive shaft up and down on the differential end, watching the pinion shaft/yoke. If you see movement up and down or side to side, you just need to have the bearings replaced. Pinion bearing failure is quite common on 9.25 differentials (if that's what you have), I've got mine being replacedthis week. I had a whining noise too. A good mechanic can take off the cover and usually see what's wrong if you can't find out on your own.

 

Can I DIY or is this somethig I need to take in?

 

Just crawl under the truck, shake the driveshaft up and down while watching the pinion shaft. Up and down movement will be very noticeable if the pinion bearing is bad enough to causea whine.If there is no significant movement side to side or in and out I'd recommend you have a mechanic check it, since the problem can't be seen without pulling the cover.