I acquired my 1969 John Deere 4020 Diesel in April 2004. This tractor had been totally gone through by Northwest Implement (John Deere) in Maryville, Missouri. They provided me with nine pages of computer printout which listed every part replaced and every adjustment made to this tractor. This tractor had been professionally painted by a man who specializes in painting classic cars.

  The previous owner of this tractor and I swapped his 4020 for my 1957 Chevy 4x4 pickup which had also been restored. We both walked away happy and a little surprised that we had found what each of us was looking for and was able to agree upon a trade.

  Since acquiring my 4020 I have bought one new rear tire to match the other new rear tire, fixed the lights so they all work correctly and rebuilt the suspension of the seat. In June I went on a 80 + mile tractor tour in NW Missouri which was a fund raiser for  Camp Quality ( camp for children with cancer). I had a blast and felt like I was also helping someone else too.

The John Deere 4020 was in production from 1964 to 1972

It was an era when farmers were doubling up field operations to achieve economies by reducing the number of trips over their fields. The 4020 had the power to accomplish this, pulling not just a disk, or a planter, but both, hooked in tandem, in the earliest steps toward minimum tillage. It pulled not just a baler, but a baler plus a bale ejector and the trailing wagon to receive the bales.   It was an 

era of greater attention to operator safety features. John Deere engineers developed Roll-Guard (r), the first widely accepted tractor roll-over protective structure (ROPS). In 1966 it was offered on the 4020 and other 'New Generation' tractors. Then the patents were made available to the entire industry so all tractor operators could have the protection John Deere engineers had made possible.

It was an era when business farming required improved traction for 'non-stop' farming. So the engineers developed power front-wheel drive, and made it available first on the 4020. And a better method of attaching dual rear wheels was developed to replace the old system of bolting extra wheels to the drive wheels mounted on the tractor's axel. A longer rear axel was offered on the 4020 so the outer wheel could be attached to the axel. To distinguish this system from the previous practice, John Deere called them 'double rear wheels'.

The 4020 saw two other significant steps in tractor evolution.  It was originally available in row-crop or standard configurations with gasoline, diesel, or LP-Gas engine (the most popular version was the row-crop diesel).  In the late 60's, demand for the LP-Gas tractors waned, and that option was dropped. Similarly, the distinctions between standard and row-crop tractors diminished; eventually the two types were blended into one.

The heart of this classic tractor was an equally classic engine with 404-cubic-inch displacement. Improved over the years with many refinements, turbocharging, and intercooling, it remained in John Deere Tractors even after the 4020 had been discontinued. The 4020 diesel was originally rated at 91.17 PTO hp."  

 Excerpt from John Deere Tractors 1918~1994 Copyright 1994 by Deere & Co.