Fixing JD 4020 hydraulic loss
JD Service Information R.84-70-2.
My notes from the microfilm version of R.84-70-2 and the bill with the current (October '98) part numbers and prices. It fixed my 4020 and several others that have asked. This replaces the worn out check valve in the transmission that lets oil drain from the front hydraulic pump reservoir. It is possible to fix the valve inside, but that requires lifting off the rock shaft assembly and cover which needs a small crane. The symptom it fixes is that the hydraulics (steering, brakes, and other uses) disappear when the clutch pedal is pushed. The computer version of this Service Information should be available at Deere dealers, but it has no illustrations.
Translation of my scribble:
Service Information: Remove the return elbow behind the transmission oil filter. (This is the line that goes to the main hydraulic pump and reservoir up front along the left side of the tractor. 3/4” ID steel tubing.)
Drill the O-ring end of the elbow 11/16” diameter deep enough to intersect with the outlet.
Tap that enlarged opening to ¾-16 UNF. Clean the elbow. Apply Loctite to the threads of the R39075 seat and install the check valve assembly into the elbow. Then reinstall the elbow on the tractor.
The original service info says the parts are: R39075 seat, D2361R ball, R39078 spring, and R39076 guide. When I bought the parts, the seat number delivered was R68553. Today R39075 is replaced by R68553 is replaced by AL71016 kit.
I've been informed and I've confirmed that the kit AL71016 contains all these parts and an O-ring (R26375). The kit fits 129 Deere models, including 840, 2155, 2355, 2040, 2450, 3040, and 3140 but it is not listed to fit the tractors covered in this Service Information. The best I can determine its not used in an elbow, but is a part of the main hydraulic pump on the listed tractors. I was not successful in finding an elbow with the threads for the check valve conversion in JD parts.
According to some 70s era Deere tractor Service Bulletins that I have, side console tractors can have the same symptoms, but this Service Information is not how they are fixed.
In the collection of Service Bulletins that I have, T69-3 page 3 , T70-10 page 3, and T71-2 page 3 have information on loss of hydraulics with the clutch pedal pushed in side console tractors, at least late 3020 and 4020. I don't have Service Bulletins after 1972 which may have more on these problems.
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Last modified December 23, 2014, Dr. Gerald N. Johnson