: What is the differnce between the series of 17's I have a series 4.
The biggest difference in most of the different series were paint and minor mechanical changes. However, there were a few major changes. The first is that the earliest D-17's had the bypass oil system like the WD series. They got the full flow system at I believe Serial number 24001. The Series III tractors were the first to have a series designation on their decals. They were also the first to have the wide cream strip running the full length of the hood (the most attractive in my book). There was a major change in the series IV tractors. They got the low pressure high volume hydraulic pump installed in the old belt pulley housing instead of the original high pressure piston pump system. This gave the hydraulic system specifications similar to other tractors. Also, this pump was fully live (not affected by the foot clutch). ALso, this tractor was available with factory three point hitch. Other changes that occurred in the D-17 series included changing from an oil bath to dry air cleaner and also the power steering went from being gear driven and located between the distributor and governor to a belt driven pump, although I don't know off hand when these changes were made. Also, sometime before the Series III tractors came out, the hydraulic oil reservoir was combined with that of the power director and they also received a hydraulic oil pump.