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Fixed flow and variable flow are two entirely different animals. Fixed flow will not work because the valve pressure port is blocked when the valve spool is in the center position. No flow is allowed to pass. If you have a fixed flow (gear) pump, it simply stalls the engine or breaks. If...

Sure, you got the PTO from me and that is partly why I don't want to see you get the wrong pump. But I'm pretty much the same with all people here, will help when I can. My purchase of the winch unit and determination to make it work has a lot to do with working these issues out too. Your...

Not having read the wrecker TM, my observations have been that they use gear pumps, off the tranny and the transfer case. They are positive displacement and not compatible with the valving of the crane that was made for LMTV and HEMTT, with pressure maintaining(compensating)(but 0-full) flow...

I don't think you understand what I'm saying about the pump. Yes the driveshaft has to be used because there is not room to flange mount a pump, but if you purchase a pump from a 5 ton 939 series, they are gear pumps...they won't work. Tell your hydraulics man you need a pressure...

Here is what I'm using. Caution when you get the pump that it's direction is correct. Oh yea...and mine is a lot less flow for smaller stuff...like my 2" cylinders that I have 25 of.

Don't overlook an important point...this system requires a variable displacement piston (or some vanes) pump, pressure compensated, and is not a positive displacement (gear) type pump. Unless that OEM pump comes from an FMTV or HEMTT, it ain't gonna work. I'll grab the pad and go take a photo...

It will be a couple days before I'm back into this. Thank you very much. I hope it helps with your project too as there are safety interlocks that make this a more complicated swap than first impression. I have the chance to get an M977 Grove from Grendel and bring it here on the trailer...

Rain...in sunny California??? Just kidding. Much thanks for your help 8madjack. Gringletaube provided a very useful link in this thread: https://www.steelsoldiers.com/showthread.php?157838-Crane-info/page2. I found the schematic on page 811 and some other useful info before that. But I...

I am still looking for hydraulic schematics for the crane winch. I have taken the winch completely apart, including the brake unit and put in new o-rings. I found the brake wet clutch pack has three chambers that oil goes in and there are 1/8" ports for them. One makes the pressure on the...

Okay. Post up some pictures when you get a chance. If you come up with a hydraulic or electric schematic, please post it.

It looks like the same crane. Grove cranes came on the early HEMTT. They replaced them with a HIAB, which is probably why the Groves are available. Safety interlocks will be some of the hardest to adapt, but it has been done. I just found a thread with a deuce with one that may have good...

There are a lot of threads on the MHC 977 Grove crane. Here is one useful post. I noted the HEMTT system is usually 2500 and maxes out at 3000. "My tank holds 20 gallons and it uses as much as 1/2 of it when everything is fully extended."

I think what you have is a Grove MHC 977, like Grendel has. They are off of early HEMTT's . It's too heavy for my deuce project. Quote from one post; "Grove made the MHC977 as a government contract unit speced out by TACOM so there are no Grove parts manuals or handbooks for it."...