I wanted to post an update to this thread as I did find the problem. It was not the speed sensor on the diff housing or the input/output sensors on the transmission. It was the actual ABS module itself. After replacing all these sensors with no luck, I started troubleshooting the CAN-BUS system with a 4 channel scope. The input voltage to the speed sensor would show correctly when I first started the vehicle. After it ran for a few seconds, the voltage would go through the roof. A good friend was able to use an old dodge diagnostic tool to check the PCM, and it was working fine. I did some more tests with the ABS module and decided I'd replace it with a used unit. I found one from a reputable scrap yard for $85. Took about 45 minutes to install and the speedo works again plus the ABS light is out. Luckily, this module must have had the right correction factor in it because my speedometer readings are correct. The biggest pain was to bleed the brake system correctly. To prime an ABS unit, you need the STAR system (or you're suppose to use one). I got around this my doing a bunch of emergency stops to force it to kick in, then rebled the brakes.