You would be testing the tranny also since the two share the fluid necessary to check operation. Preventive replacement and service of the most common problem makers is not expensive nor time consuming when the unit is out of the vehicle.

J type OD or D type OD have different service and replacement requirements.

With either type, remove OD from tranny and replace the actuating piston seals. A lot easier now than if the unit is in the auto. Once the OD is off, you can look "inside" and see if there are any problems with the sliding member (cone clutch).

J type: remove and clean the solenoid internals, replacing the internal O-rings before any use. Many miles and poor maintenance cause many problems with these which can destroy any OD returned to factory specs except for the solenoid.

D type: remove and check the operating valve for clean and in the corrct sequence. It should move freely in the bore. Adjust the solenoid for proper stroke AND current draw at operatitng position. You will need an amp meter for this adjustment. Activation current is 13 amps while holding amps is only around 2 amps. If not adjusted properly, the solenoid will burn out or the wiring will get very hot.

Duane