936A2 Crane Motor Case Drain

[charlesmann]

I cant seem to find the MWO or the thread about the MWo for the crane winch motor case drain MWO. I did use the search engine, probably not using correct key word search, and i looked in the TM section but nothing on the case drain. Any help will be greatly appreciated.

 

[M35A2-AZ]

When I first got my truck the HD motor on the crane was leaking. I had it rebuilt and after I started using it started leaking again. The shop said I needed a case drain. The motor I have is made by Parker. I put a case drain on it and ran the line over to the HD tank, I also put a one way chuck valve on the line.
The Parker motor has a little plug on the bottom for a case drain.

 

[charlesmann]

When I first got my truck the HD motor on the crane was leaking. I had it rebuilt and after I started using it started leaking again. The shop said I needed a case drain. The motor I have is made by Parker. I put a case drain on it and ran the line over to the HD tank, I also put a one way chuck valve on the line.
The Parker motor has a little plug on the bottom for a case drain.

where did you put the fitting that drained back into the tank? If i had the mwo, i could reference it for fitting placement. Im heading to hyd shop now to get an npt to jic then a 90 fitting with a m swivel and fm nipple and get 8’ of -4 low psi hyd line and run it into the tank near the tank fill port by drilling and tapping the doubler plate for the fill port and threading another npt to jic fitting, preferably a 90 fitting with a nipple.

 

[M35A2-AZ]

I think I took the fitting off and drilled and taped a 1/4"pipe hole. I have tried to find photos of the work and I can not find it.
Good luck with it.

 

[charlesmann]

I think I took the fitting off and drilled and taped a 1/4"pipe hole. I have tried to find photos of the work and I can not find it.
Good luck with it.

took what fitting off? Where was the fitting located?

 

[M35A2-AZ]

I went out and took some pics of the fitting. This is what I did. I think I did a post of this many years ago.

 

[KN6KXR]

IIRC there is no MWO for this. The issue was found in the civilian sector. What happens is that without an inter seal weep hole (or it's plugged) the motor fluid gets pushed out the shaft that goes in the reduction gearbox. The gearbox fills with hydraulic fluid (and of course the gear oil that's in there) and the case leaks out it's OEM weep hole on the front cover.

I first found this when operating the crane and observed it leaking all over whenever I ran the hoist. I then found the thread here someplace that outlines the problem. I temporarily ran a line from the weep hole to the hydraulic tank fill cap as a test and confirmed this. All 1/4" I believe.

My tank (1991 M936A2) has a bung with a plug on the rearward facing side. When I had the tank drained for other maintenance I installed a elbow and 1/4" shutoff valve. Later on I hand bent some 1/4" copper hard pipe and ran from the motor, along the boom, to the pivot using a grease gun 1/4" flex pipe, then back to the tank to the valve I had installed. I did not use a check valve there is little to no pressure there it's just a drain from the pump seal area. Since then I've had no issues leaking hydraulic fluid in to the hoist reduction area.

There are two different motors that were used on the wrecker crane platform. I can't recall right now the older one but the newer one is the Parker. The older one did not come with a case drain but the Parker did. The military rolled out the Parker as a replacement and I think they never ran a drain but left them plugged. By the time they caught on to what was going on the end of the product had come and they just moved on. They did this with a lot of stuff my data plate actually has two different tire pressures front and rear for the CTIS as if they meant it to have a 2 channel system but it's equipped with a single channel system.... They just never got around to it.

I have one of each motor style on my 936. The older one on the rotator and the Parker on the hoist. According to the TM's they are interchangeable and by the looks they would. Someplace I have some drawings I've collected of these parts and can snap some photos if you like. Off the top of my head that's the best I can remember hope that points you in the right direction.

 

[charlesmann]

@KN6KXR
I ran a 1/4” low psi hyd hose from the case drain port, to the return line elbow at tank. I havent noticed anymore fluid running out of the rope drum (seals are shot) or out of the rgb vent. There might still be a minute amount that enters, but i have not needed to crane but a couple times since i added the drain line. I guess i need to tear it down again and this time, replace the output shaft seal. I did replace the square drive shaft seal, but even the parker guys claimed they couldnt find the output shaft seal. Iv got another motor i havent rebuilt (leaking from the square drive) yet and honestly cant remember where i put everything.
There is a brass split ring with a concave on both sides, that is suppose to go in the motor, but hell if i could find where it is suppose go.