Alright, here we have a 1999 5700 Vortec Chevy Tahoe 4x4. It has about 170,000 miles on it (it was a workhorse for a local grading company) that's suffering from three distinct and seemingly unrelated problems, but they all occur at the same time. It started with the anti-lock brakes kicking in at low speeds. I was advised to remove the wheel sensors, clean and re-grease them with an anti-rust grease. I did this despite the sensors and the housings being seemingly immaculate. This did however seem to stop the problem. Only two days after that though, I braked and the ABS light turned on. The transmission went into what I can only guess is limp mode. When in the normal overdrive selection, it starts out in third and gets no acceleration after about 3000 rpms. Same thing if you manually shift it into second or first. 4-wheel drive will engage but the vehicle will not move. Also, the speedometer would move seemingly randomly even when the Tahoe is stationary, and now will not move from zero. The problem seems to also start randomly. Normal operating temperature can be reached and exceeded without any problems normally, all though the problem will not start with the vehicle cold. Any ideas?