Tried the traditional 2 man approach, and then used a mityvac attached to rear bleeder. I get absolutely no fluid. I have come across a few posts that say something about the ABS proportioning valve has disabled the rear brakes, and I need a scan tool to cycle the valve. Any truth to this?

I just replaced the long line that runs from proportioning block on frame rail to the rear brakes.

 

if the abs valve was allowed to run dry then yes you need the DRB tool to cycle it and get a proper bleed

 

I replaced the same line with no such problem.. if it was a used line are you sure that fluid can pass threw it??

 

The proportioning valve on the frame bey the starter and is different then the ABS pump motor. If you ran the brake fluid all the way out of the master cylinder then you will need the DRB-II. Now I would remove the brake line from the rear axle splitter and see if you can get fluid out and flush any debris out. If it works then you probably have bad rubber lines to each wheel. If you get pressure but no fluid then most likely the proportioning valve is bad.