Read this thread
, then click my signature link & look in the 8.8" Axle album. Pull your ABS sensor, clean off any metal filings, & inspect the tone ring thru the hole. If you chock BOTH front tires front&back, lift at least 1 rear tire, & put the trans in N, you can spin the d'shaft and inspect the entire tone ring for damage or looseness. If there are a lot of filings on the sensor, you should open the rear cover & find out why.
If all of that checks OK, then it's probably the PSOM dying. They're known to occasionally. Just find a used one. If you can't find one locally, e-mail me. I have a few.