Jd 6420 tractor with 12r syncroplus transmission overheats after 3 hours of operating. Tractor has 1500 hours. Fresh hydraulic oil and filter change. The manual shows a clean out screen at larger filter. There is none there. Heat gun reader trans. Temperature gets up to 230f. Anyone have any ideas? Thank
Jd 6420 transmission overheating
- Thread starter Pwquist
- Start date
RickB
Super Star Member
- Joined
- Sep 18, 2000
- Messages
- 15,205
- Location
- Up the road from Dollar General WNC
- Tractor
- Just a Scag
Those tractors are notorious for plugged radiators & hard to clean oil coolers. Check the airflow through the heat exchangers in front of the cooling fan. If it has a viscous fan clutch, make certain it is functioning properly.
What are you doing with the tractor when it overheats? What implement are you using? Have you done the same job in the past without overheating? The 6420 uses engine coolant circulated through the cooler which is located behind the engine and in is in a circle around the driveshaft. Be sure too check the lines to and from the cooler to see if there are any kinks or restrictions. Also be sure to check the radiator and screens for unobstructed airflow. Check the upper and lower tanks on the radiator. some of the early 6020 series had plastic upper and lower tanks that had problems. the aluminum upper and lower tanks were more relaible - The cooling system is a split system. the engine portion of radiator runs at 180 degrees. The trans oil cooler, engine oil cooler, and heater portion of radiator runs at 140 degrees. The earlyu radiators tended to allow the "hot" and "cool" sides mix together resulting in transmission overheating.
