3720 hydraulic major leak

   / 3720 hydraulic major leak #1  


Veteran Member
Feb 21, 2005
Central WI
Working my 3720 today clearing snow at our cabin woods (mostly pushing/dozing with the loader) I came to the realization that my loader was operating very slow and sluggish with lots of air. Power Steering and hydro travel seemed fine. Took a break for lunch and I heard a hiss and saw fluid spew from the pump area on the engine. Upon closer examination I found that the at the top of the pumps is apparently split. Curious if anyone else has had this happen?

My machine is one of the earliest built and many years back I reported that when I pushed the hydro hard the loader would let you know that it had air traveling through it. Maybe I'll get lucky and this wil fix that issue.
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   / 3720 hydraulic major leak #2  
Yep... could be that you've had a defective hose at the pump connection - hardline junction; all this time. Something for other user's to consider... By the way, how did you resolve the front driveline issue? Was it the front axle/differential adjustment that caused the split pins to fatigue?


   / 3720 hydraulic major leak
  • Thread Starter
I'm thinking in time others will have isues as well. Minor issue, simple fix, but down for the count. When I restarted after my lunch it continued to work in it's limited capability. I went back out and finished the driveway then shut down again. Started up to load up and left it idle w/o park brake. Started to roll away fast which it never does. Oil getting low obviously. I just managed to get the loader up and drive it on the trailer. When I got home the rockshaft wouldn't lift up. Added a quick gallon (I couldn't see where a gallon had actually come out) and had to rev up to get rockshaft up then loader barely came up and hydro groaned, power steering chattered, etc. Hopefully the part is available quickly as it's time to load a round bale in the next few days.

On the driveline it was dry splines. The shaft is open and has a sleeve/coupler at each end. With no support on any of it the vibration and corrosion cause wear. It wore to a point that it started to skip. For a quick fix I flipped the one end for end as the splines seemed to wear on the pinion shaft itself and the coupler on the pinion end as well. The driveshaft was near perfect. I think I ended up replacing the one sleeve and I made **** sure to smear some EP lube on the splines.
   / 3720 hydraulic major leak
  • Thread Starter
$14.88 for the manifold and I'm back in business. My dealer contact said not in stock, but he had one at home. Had I called him Sunday I could have had it fixed then already. The old hose had a coil spring inside. The new one did not but I dug it out and transferred it over.

So when I went to put back together the port for the rear pump was misaligned. It seems the suction tube sopport tab was bent causing it to put stress on the manifold. It was pretty easily tweaked back in alignment.

A quick run up and down on the loader and rockshaft to purge the oil and ready to rock.