:D
AND THE WINNER IS...
CODE58
I took the RX int to the brake shop that did the brake work for me about a month ago. They test drove it, put it on the lift and removed the wheels/rotors off the back. And as code58 suggested, the emergency brake shoes were both jammed and locked up inside the rotor (drum). They freed them and the problem was solved (good to drive). Because they had done the brake job they did not charge any lift fee or time charge. The e-brakes still had plenty shoe left and evidently they were heating up and would build up some sort of resonant frequency to cause the shudder after a mile or two and then repeat the process after I stopped -- thus the weird on/off problem.
Thank you code58 for your suggestion!
Now, the brake shop also said the "cables were jamming up" and quoted me $500 P&L (OEM parts) to replace the cables. Yes, that's 500 US dollars, not pesos. I declined the offer. They also told me that "squirting lubricant, etc." on/into the cables would not fix the problem, based on their extensive customer wallet bilking experience. I told them that if my wife kept her little foot off the darn e-brake pedal until I could disconnect the cables, I would be just fine. I then explained to my wife that unless she was parking the RX in SanFrancisco on a street with a 70 deg. incline that a AWD probably wouldn't roll away.
Thanks for your posts. Thank GOD it was not the differential or trans. All the trans failure post on the forum freak me out -- this 99 RX is still not paid off and I've got 107K+ miles on it.
Best regards to all!