4720 hissing sound when pto under load

[jcalla]

john deere 4720 pto hissing sound. any ideas?

 

[beenthere]

Anything getting hot when that happens?

 

[Tx Jim]

It appears from viewing 4720 parts catalog that your tractor has a hyd engaged pto clutch/brake. I suggest to determine if your 4720 has a pto hyd test port so one can check pto clutch operating pressure.

 

[Brown Dog]

Make sure hyd Rear rear remote levers aren’t stuck & report back.
I had this happen with 4700 & 4720 I use to own.

 

[jcalla]

I have checked rear remote scr's & none are stuck. This just seemed to happen after I got into some real heavy grass and did not ease up right away. I have used it since and it runs ok until I get a load on it. Then it hisses like fluid is bypassing a port and also the engine pours out black smoke like its really under load. Maybe the PTO brake is engaging when it should not. It sure would be nice to find some hyd ports where I could check pressures.