M925A2 Hydraulic System Mods

[CIH7777]

Just picked up my first M925A2 with the Cummins 8.3 today. It is a 2012 rebuild with less than 400 miles so it does not seem to have much of any wear on the main components. I have some mods I would like to do to it like adding a 2 1/2 receiver (possibly the Curt one I currently have on my M35A2) and auxiliary hydraulics to run a live bottom pull-type trailer.

I read thru several pages of posts about adding auxiliary hydraulics on the existing hydraulic system but did not notice much detail as far as photos or what parts I would be looking for. I hear the hydraulic pump on the M939's can produce a lot more gpm/psi then they are rated for but the control valve, relief valve and reservoir size limit this. I could possibly change any of these out with components that will give me more capacity if needed. I am looking to "T" in someplace after the hydraulic pump and add 1 pressure line to run the trailers single hydraulic motor and as 1 more line as a return to the reservoir. Any ideas or details from someone who has successfully done this already?

 

[74M35A2]

It won't be as easy as that, because all your pressure and volume will bleed off through the winch bypass in the control valve. Also, the 925 hydraulic pump does not operate when in "drive" and at a stop, so not sure when you need hydraulic power to your trailer and when not.

Maybe easier to simply add a belt driven hydro pump, tank, and such. Otherwise, you will have to ditch the single handle control valve, and install a multi-station parallel D05 type hydraulic valve block, with an 1800psi pressure relief, 24V motor spool solenoid valves, and a solenoid type bypass valve in the manifold to develop pressure when either solenoid is activated. Or, do this with a 2 valve mechanical system, but just to T into the pump outlet won't work unless you block the flow to the winch valve, of which then you would need a relief on your new line, rated to flow up to 25 GPM I think.

 

[CIH7777]

The belt driven hydro pump would be the best option but I have not found any so far that produce at minimum 14gpm at 1800psi at the rated engine rpm of the 8.3 Cummins....or better yet a good setup of one installed on a M925A2. I agree, the belt driven pump would make my live bottom trailer a whole lot more useful with it. If I have to go the pto driven hydro pump route I would probably just isolate the winch somehow with a couple valves as I will not use it the same time as the live bottom trailer. If I can complete the whole install for less than $2K, I could possibly keep both the winch and aux hydraulics operational at the same time

Update...Just spoke with a Muncie dealer and supposedly none of their belt driven hydro pump models can produce the min. flow/psi I need but they do offer piston pumps that are driven off the crankshaft so I'm looking into that option right now. I might have to do some mods to the radiator position and front grill though to provide enough room for the piston pump/shaft assembly. Has anyone tried this type of mod on a M925?

 

[74M35A2]

http://www.northerntool.com/shop/tools/product_200329778_200329778

 

[tobyS]

I'm bringing this up to ask a hydraulics question.

Why can't one come off of the tank port on a 925 winch truck valve for the pressure port of another open center valve (dump and plow operation), if they are close to the same gpm capacity?

That would be a series configuration. Or conversely, put the new OC valve in front of the OEM winch valve. Not a Tee... in series and with pressure rated tube (hose) for the volume (same as pump to valve size).

Note there would be need for more tank reservoir.

 

[big block 88]

I wouldnt see why you couldnt. Only issue i could think of would be volume of fluid with all the lines and valves. That said if you are isolating each application that would be a moot point.

 

[snowtrac nome]

as a note to self the crank drive pump might require the removal of the winch

 

[rhurey]

I wound up putting a selector valve instead of doing this. Mainly because the crane I was mounting had a lot less flow through it's valves than the winch valve did.

 

[Jbulach]

I'm bringing this up to ask a hydraulics question.

Why can't one come off of the tank port on a 925 winch truck valve for the pressure port of another open center valve (dump and plow operation), if they are close to the same gpm capacity?...

....Note there would be need for more tank reservoir.

Is that what power beyond means? Or is that a closed center hydraulic system term/problem only?

Reservoir size should be fine once the system is full the fluid level won't change running a motor, except for heat expansion.

 

[Jbulach]

...and auxiliary hydraulics to run a live bottom pull-type trailer.

I read thru several pages of posts about adding auxiliary hydraulics on the existing hydraulic system but did not notice much detail as far as photos or what parts I would be looking for. I hear the hydraulic pump on the M939's can produce a lot more gpm/psi then they are rated for but the control valve, relief valve and reservoir size limit this. I could possibly change any of these out with components that will give me more capacity if needed. I am looking to "T" in someplace after the hydraulic pump and add 1 pressure line to run the trailers single hydraulic motor and as 1 more line as a return to the reservoir. Any ideas or details from someone who has successfully done this already?

Your pump should be putting out 27 GPM at 1800 engine RPM. The winch control valve is shimmed to limit the system pressure to around 1750 PSI. However the pump is rated at 3000 PSI, but I don't know the max PSI of the vale. Mine has lived after shimming to 2500 PSI for some time now.
As far as your plumbing, I put this selector vale on mine, after the winch control valve in the two lines that run up to the winch. This basically gives you the ability to switch between the winch and your add on.

Remember to never exceed 1800 engine RPM when your PTO is engaged. Also, I put a pressure gauge on the winch wind side of the hydraulic system, so I can try not to exceed the winches maximum PSI of 1750 and can also see how much pressure my dump cylinders are pushing.

 

[rhurey]

I used the same selector valve, but in 3/4" NPT and with a pressure relief after the pump before the winch control valve.

Feeding the valves for the crane on the back.

 

[tobyS]

"Is that what power beyond means"....probably, but I'm not sure the context. No, not a term often used with closed center.

By putting another open center valve in series, the valve you show is eliminated and to a certain extent, one can make coordinated moves. Like say raising the blade and turning the blade at the same time.

I just was hoping to confirm if others have added valving in series to expand our conversation. I can't tell from the pictures on this thread, but his valving does appear to be in series from what I see (the reason I made a post on the older thread). Since I see his return line intact, I would think his new valve was after the pump but before the winch valve.

Of course you can put a second diverter valve like you have for the dump...not a bad price, just may not be necessary.

 

[tobyS]

as a note to self the crank drive pump might require the removal of the winch

Make a second note that the hood mount and radiator are also in the way (major modification). I'd really like to come off the crank for another, high HP (sawmill) application...but tooo much in the way.

 

[tobyS]

I used the same selector valve, but in 3/4" NPT and with a pressure relief after the pump before the winch control valve.

Feeding the valves for the crane on the back.

So the pressure relief dumps the excess flow when it reaches set pressure. Only thing about that is heat. Flow under pressure without doing work makes heat...and can be a lot, especially with a small tank. Have you ever felt your tank or hoses or valves when it's been setting running but not working?

 

[rhurey]

So the pressure relief dumps the excess flow when it reaches set pressure. Only thing about that is heat. Flow under pressure without doing work makes heat...and can be a lot, especially with a small tank. Have you ever felt your tank or hoses or valves when it's been setting running but not working?

Right. Flowing with all valves centered the system shows 500 PSI when sent to the crane. The crane was rated to 2500 PSI, the winch on it to 1K. I wasn't sure what the valve on the crane was rated for (2nd hand purchase) and since it's at the back of the bed and a long ways off I figured I'd play it safe and dump extra pressure at the selector if I went above 2,000. The valves on the crane have another pressure relief set to 1K. (Which I need to re-do so the crane and the winch can get different max pressures)

Just running through the crane and not working the system stays cool.

 

[rhurey]

Is that what power beyond means? Or is that a closed center hydraulic system term/problem only?

Reservoir size should be fine once the system is full the fluid level won't change running a motor, except for heat expansion.

http://www.baumhydraulics.com/files/infobuild/terms_hydraulic_control_valve.pdf

Worthwhile read.

 

[Jbulach]

...I just was hoping to confirm if others have added valving in series to expand our conversation. I can't tell from the pictures on this thread, but his valving does appear to be in series from what I see (the reason I made a post on the older thread). Since I see his return line intact, I would think his new valve was after the pump but before the winch valve.

Of course you can put a second diverter valve like you have for the dump...not a bad price, just may not be necessary.

I'm very curios if adding another valve will work also.

It's not very hard to do but... you lost me here, what pictures are you referring to? Old thread? And who is "his" that has the valves your referring to?

I found some reasonable priced, 25 gpm, 24 volt, solenoid operated, selector vales on the web.
I considered mounting one up by the winch. I would use it to switch between raising my snow plow with the winch and angling the plow with the hydraulics. I have no need to raise and change the angle at the same time

 

[tobyS]

So you are dumping 500lbs. Do you notice the pressure go up when a valve is being used? It should go to the relief setting when the valve closes the open path and diverts to a function (that can't take full flow, causing pressure to rise.

I'd rather have a series with full flow (open center) and orifice down (and or pressure control) my components.

I made a $8k mistake in 87, but at higher pressure and 70 gpm. You could fry an egg on the tank.

 

[rhurey]

The pressure gauge at the input to the crane's stack is 500 PSI. The crane's valves are all OC and that's just the pressure with no work being done. (or my gauge is crap, but...) 500 is what I assumed the restriction from the system of having a 1" pump pushing through a 3/4" selector and down ~15' of 1/2" hose to a 3/8" valve stack and back to the tank was.

The pressure at the crane's valve input rises to 2K when the crane is in use. The relief at the selector dumps at that point. The crane's valve's internal relief opens at about 1200 PSI. (You can hear the flow change, and see the input keep rising till the selector's relief cuts in).

 

[tobyS]

I'm very curios if adding another valve will work also.

It's not very hard to do but... you lost me here, what pictures are you referring to? Old thread? And who is "his" that has the valves your referring to?

I found some reasonable priced, 25 gpm, 24 volt, solenoid operated, selector vales on the web.
I considered mounting one up by the winch. I would use it to switch between raising my snow plow with the winch and angling the plow with the hydraulics. I have no need to raise and change the angle at the same time

Sorry, got mixed up with another thread that showed (I think) a valve like you want in series, like I describe. I thought it was page 1 in this thread, but am mistaken.

Read the "power beyond" that rhurey posted. I'm not sure about the sleeve they speak about but it surely can be done. Flow and pressure can be controlled at each spool...probably blocked ports when in neutral.