I have a 98 dakota with 318 engine with 140,000 miles. Lots of rear end noise almost a grinding noise but definitely a VERY audible whine. I think it's probably the ring and pinion that needs replacing. The noise is only under acceleration and constant speed. Starts at 15 MPH and goes all the way up. No noise on coast. Anyone ever change these themselves or is this a job for an experienced shop?

That sounds like the differential going south. There are a few tools you'll most likely need. You'll also need to have some knowledge about pinion bearing preload specs, and how to properly shim the differential case, etc. I think a good chiltons or haynes manual should point you in the right direction if you choose to do it yourself. If you want it to last a long time, however, I'd suggest taking somewhere where you trust the mechanic/technician.

dont forget about the U-joints, although they usually make more of a squeaking sound

I also have a 98 dakota with the same rear end whining noise. only does it when you accelorate. someone told me it was the rear axle and bearings. how costly can it be to have someone else do the work?