I took some more waveforms the other night and am still stuck on how much different the LR is compared to the other 3. I spun the tires using the engine so I could get a faster time/div on the scope to see if there were any glitches over a full 360 deg rotation of each tire. The waveform is smooth for all and even for the noisy one. The reason I can say this is because as you increase the rotation speed the amplitude of the sensor signal increases too. With a much larger amplitude I had do adjust the volts/div on the scope to accommodate the whole signal and when I do that it squashes the noise too. All tone rings look good.
My theory is that there's circuity on the sensor inputs of the controller that automatically scales the signals (similar to what I did with the scope) as rotation speed increases. Usually they're called AGC circuits for Automatic Gain Control. With higher speeds and higher amplitude the signal to noise is good, but as you slow down the signal gets lost in the noise and that's when the ABS starts to kick in.
The left rear is the fartherest away from the controller, but it looks like the wire goes over to the passenger side to meet up with the RR and head up to the controller. It could only be a couple more feet so wouldn't think that much noise would be added. I also thought that maybe one of the wires got shorted to chassis and was almost sure of it for a while unit I figure out I had an earth ground loop. Lesson to anyone using a professional lab scope. Those scopes tie the probe ground reference to earth ground. Believe it or not I had made a connection from one side of the sensor that the probe ground was connected to, through the scopes earth ground to the wall outlet, then back through my trouble lights earth ground tied to the metal bulb shield with a hook on it that I had hanging on the glovebox metal latch hooky thing. when I used a DMM to measure the sensor leads to chassis, it followed that funky path and F'd up my brain for a while. After I figured that out I found I had full Meg ohms to chassis, so no chassis shorts.
I decided to buy a $20 ABS sensor to test outside of the hub to see if the noise is still there.
I will look into your suggestion Paul about the routing around the steering column, but not sure why that wouldn't affect more than just the Left Rear.
Thanks for you support guys. Why do I always have to get the freaking out of ordinary problems. I should tell you my Town & Country torque converter lock problem someday.
Kurt