Speedometer fluctuating causing tranny to act up

[jwilley]

I have an '02' Silverado 2500HD 4x4. About a week ago the ABS lights started coming on. Then the speedometer started fluctuating by 5-10mph. Last night we were driving and the speedometer started bouncing back and forth by 30-40mph each direction and when it did this it began down shifting the transmission. We would have to put it in neutral and back in drive to get control. Took to parts store and read codes. Stated all abs wheel sensors missing or erradic. We already changed the vehicle speed sensor. But since it has alerted all wheel sensors still after changing the VSS I was thinking it could be the EBCM (electronic brake control module). Any comments, experiences, ect. are welcome.

[jwilley]

After looking around this sight more I feel I should add that my wife drove my truck in 4h during snow for about 5-6miles at around 45mph. And there is a noticable ticking sound when in 4h and low.