Need parts for a John Deere 8420? This 8020 series tractor is covered here with more than 200 items, among them trailer couplings, lighting and electrics.
An 8420 often works from first light until well after dark, which makes good lighting and a decent seat part of the toolkit rather than a luxury. This page brings together more than 200 John Deere 8420 parts covering lights and seating, hitching, cooling and engine wear parts. They come from GRANIT, ROCKINGER, GRAMMER, Walterscheid and HELLA.
LED work lights with a wide flood beam light up the headland when you are ploughing or mowing at night. For the cab there are air suspended tractor seats, including a GRAMMER Maximo Professional.
If an air seat keeps sinking, check the air hoses and the compressor connection before replacing the bellows. A small leak at a fitting or a split hose is a common cause, and with the engine off you can usually hear it hiss.
At the back of the tractor you can pick from ball drawbars, drawbar frames and connector heads for the trailer air brake. If you pull a trailer with forced steering, the matching ROCKINGER parts for the drawbar frame are here as well. PTO shaft ends complete this group. Replace a stub whose splines are worn or damaged in good time, otherwise it also wears the hub of every driveshaft you slide onto it.
If the alternator charges weakly, check belt tension before condemning it. A worn V-belt tensioner lets the belt slip, and even a healthy alternator then cannot keep the battery topped up.
Thermostats, gaskets, seals and sealing rings keep the engine tight and at the right temperature. Whenever you fit a new thermostat, renew the gasket or O-ring of the housing too and bleed the cooling system properly afterwards, otherwise an air pocket can make the gauge jump around. You will also find alternators, V-belt tensioners, engine sensors and a gasket for the turbocharger oil return line.
Read the model and serial number from the rating plate and compare them with whatever is marked on the part you are replacing. Seals and gaskets rarely carry anything legible, so make a note of exactly where the old one sat. On alternators and other electrical parts the reference number is normally on a sticker or plate on the housing.
The 8420 belongs to the 8020 series. Its sister models each have a dedicated page: John Deere 8220, John Deere 8320 and John Deere 8520. For any other tractor from the brand, go to John Deere parts.