MM 670 Super

Jersey Jim

New User
Just purchased a 1969 MM 670 Super Diesel with 3 speed torque and closed center hydraulic. Was there an update for the hydraulic pump so it did not over heat? Also, what hydraulic oil is used in the hydraulic system, 3 speed torque, and transmission? Would Hytran work? Thanks
 
My 1050 closed center runs hot if I'm not using the remotes a lot, I run a bypass hose from one remote outlet to the other and snap the remote lever open and let it circulate ,it keeps it a lot cooler,if i'm using a implement that only needs one set of remotes I use the second set and center the bypass when I need pressure on the implement,probably not the perfect solution but it works for me,operator manual says SAE 80 in rearend/torq and hyd oil in the hydraulic system.
 
As long as there isnt a oil supply pump on the rear end the 80w-90 oil should work otherwise it might have a problem pumping it in cold weather. Im not real familiar with the 3 speed torques. Ive used universal hyd / trans oil in my G950 hydraulics and it seems to work just fine.
 
If the hydraulics get hot, odds are good that the Gressen valves are leaking, causing the pump to constantly run. They are originally very tight tolerances. I have heard of people getting them resurfaced.
 
Where can I find more information about the Gressen Valves? Where could I get the valves resurfaced? Thanks
 
The compensating valve is mounted on the back of the pump. It is suppose to adjust the swash plate in the pump for the amount of fluid needed for the hydraulic system at any given time. First plug a gauge in one of the outlets, and see if the pressure is within specs. If it is and the pump feels like it is laboring, there is an adjusting screw plug at right angle to the pump. It is sealed with a locking wire unless it's been messed with. back the screw out and see if the pump stops laboring and or if the pressure drops on the gauge. Basically what I am saying is when the pressure gets up to specs the pump is suppose to go into a neutral state and just maintain set pressure. If changing the adjustment doesn't have any effect remove and inspect. Also as was stated before if you have leakage some where in the system and fluid is squeezing by, it will heat up the fluid. I have only had to work with a couple of units. There are others out there that are much more knowledgeable that I am.
MMDEL
 
I dont think there are too many more knowledgeable than you Del. We are
still waiting for "the book" :)
 
Alan you make me Blush. I have not worked on many closed center systems to know all the ramifications.
MMDEL
 

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