First off, I am NOT a tractor mechanic. I have worked on cars, trucks, over the road trucks, Jeeps, motorcycles and stationary engines all my life. I guess I have let tractors intimidate me to the point that I basically go brain dead when I am confronted with an issue on my old 4020. I'm getting better though.
Not a question, but a discovery I just made. Later model, 1970 4020 SN 227*** alternator went out. I looked at the alternator and the only tag or marking on it was a John Deere rebuild sticker. Asked around and was told it was a Motorola. I didn't know different so I set about looking for one. Ordered one and when it arrived, it was nothing like mine. Sent it back. Called John Deere dealer and was told $242.00 + $70.00 core since mine had a cracked case. Not so fast! I drove Oldsmobile cars from the '70s through the early '90s. I started thinking, that alternator sure looked a lot like ones I had replaced on my Olds through the years. Looked on Amazon, saw AC Delco Professional line factory re-mans with 2 yr warranty, free shipping, $37.25, no core charge, $7.00 coupon, final cost $30.25. This is alternator is sold by AC Delco through Amazon. Fits perfect. Works perfect. AC Delco part number 334-2114. Look it up on Amazon or AC Delco.
By the way, John Deere would only warrant theirs for 6 months if I installed it, 1 year if a mechanic installed it.
This adventure was definitely a confidence builder. I now have a technical manual for it and read it every spare moment I have.