Good day everyone. I'm a newbie to this forum and not very good with computers. I'm a retired grader operator and love fixing up old tractors to keep me out of trouble. I have recently purchased a 1948 allis chalmers w speed patrol grader. I'm having lots of trouble finding a copy of the owner operator manual to find out what the gear box under the tractor with a sprocket attached to the transmission and how it works. one gentleman said probably to do with what position or angle the blade is set for grading and I think he is correct but I'm not finding anything on this tractor. I do know it's a wc tractor with a front end extension added to it IE-3500 is the number on the serial number tag. thanks any info at this point would help thanks