1969 4000 industrial sounds like a 4500. I had one for 17 years. It had the 4 speed power reverser. I assume yours is the same. It has a torque converter. The power reverser {Forward, neutral and reverse) is controlled by a lever on the dash on the left side of the steering column. The 4 speeds (available in both forward and reverse) is a mechanical gear set (non-synchronized) controlled by a shift lever on top of the transmission case (between your legs). To shift the mechanical 4-speed, place the power reverser lever on the dash in the neutral (middle) position and shift the gear lever on top of the transmission.
I found this tractor to be amazingly strong and reliable. Sometimes I wish I still had it for the bigger jobs.