Green needs education on Gold: MM GB Hydraulic system

bhaack

New User
Good day all,

I need some wisdom from you on MM Hydraulics.
I have a GTB and a GB with a single lever hydraulic system. 1 set of outlets that would control 1 hydraulic cylinder. I have some implements I'll pull with either of them and both tractors behave the same. For instance, if I hook up to the 18' miller rod weeder with either of them, I can lift and lower the rod ok with the tractor hydraulics, but as soon as i return the control lever to neutral, the rod falls. It's acting like the hydraulic spool valve is leaking to return and won't hold pressure in the cylinder against the weight of the machine.
I can't find any info on the valve used on a GTB or the GB. What other model used the same setup? I think I need to reseal this vavle, and would like some idea what parts I need before I rip into it.

Thanks~
Brendon
Tri-State Antique Engine and Threshers show
Bird City, Ks
 
They are working the way they are supposed to. Moline "uni-matic" hydraulics do not have an internal check valve to hold pressure. They are designed to be used with a Moline cylinder, which had the valve integrated. This allows the hoses to never have pressure, and are always easy to hook up. Also, the ram will not drop if the controls are bumped with the engine not running. This actually was a fairly awesome design if it caught on. You have a couple options. One would be to buy a Moline hydraulic cylinder of the era (usually about $50-$100). The other option would be to plumb in a type of chekc valve in the hoses for the remote. I believe they can be bought new. Or I may have something used laying around.
 

Working as they should.
Ok. New one for me, this is the only tractor hydraulic system that i've run into that does this.
the rod has a deere cylinder on it, the sweeps have a standard cross cylinder on them.
I'll get some checks for it and put them in the lines before the couplers on the tractors. Those implements get pulled by more than just MinniMo's.
 
This might be a dumb suggestion but could you use some of those snap on collars of various widths on the cylinder shaft so you can control the depth?
 

As Chris mentioned, The Moline hydraulic system requires a Moline cylinder in order to work correctly.
Two of my Moline tractors have aftermarket hydraulic systems, so this is not a factor. On a third, an aftermarket spool valve was plumbed in, bypassing the factory set up, in order to run a loader.
 
Oil has to flow both ways in both hoses to raise up and down, you can't put a check in a hose or it will block the flow when you want to change direction. If you want to use any other type cylinder on these tractors, the best way is to plumb a double acting valve (with lever) direct from the pump. (Take the pressure hose from the pump off at the hydraulic box, run a line from there to where ever you mount your valve and hook it to the IN side of the valve. On the OUT side of the valve run a hose back to the box where you took the first hose off. Then you can remove the two hoses with the couplers and place them on your new valve, and plug the old outlets at that little block or you can leave them on and put new hoses and couplers on your new valve.) How ever you must buy a valve with a pressure relief valve in it or you will dead head the pump when your cyl gets to the end of the stroke and will blow the pump.
Years ago there was a block valve with a shifting spool that you mount at that small block where the two coupler hoses are plumbed at the steel lines, but I haven't seen one in years.
To be extra safe it would be a good idea to check the pressure setting on your new valve.( Later systems have much higher pressure and you don't know how it is set.) Plug a gauge in the outlet to check. At the time these tractors were built, the going pressure was 1000 lb you can fudge that a little. But if it raises what you want it will save wear and tear on the system to leave it in that range.
 
Yea, I'm going to replace the MM control valve with a standard open center valve, like every other tractor on the planet had, cept deere.
I know it won't be the way MM made it, but I'm not worried about that. I need this to work without MM cylinders.
 
Yes, but it makes it a pain to go down the road with, always having to have someone hold the lever while someone else puts the transport lock in. (10 more snap stops)
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top