4650 PS pto brake

[Craig C]

Hey guys, I don't have a service manual for a 4650 but looks like I will be needing one. The pto brake won't stop the pto. I haven't checked the brake pressure yet, but assuming it is the break it self. Where is it? Looks like it is a set of discs and plates just like the engagement clutch according to the online parts catalog. Just wondering how big of a job it is.

 

[Cliff Nelson]

Depends if mfwd or 2wd as to how big of a job. MFWD is a double split to repair the pto brake as the mfwd drive gear is tight to the brake pack. 2wd you can get to the pto brake with splitting at the main clutch. It"s a big job either way. Pto brake disks are likely broken/burned causing your problem.

 

[Craig C]

It is a MFWD. Sometimes it holds and sometimes it doesn't. I can live with it as long as it doesn't try to turn the grain cart while disengaged.

 

[tim s]

I had one like that in here last spring, it came in for the PTO lever not staying in,, others had worked on it replacing the control valve housing, but it didn't help, I split it and found the clutch housing was worn bad where the sealing rings ride, i air checked the brake and it worked well, but after putting it together it would not stop the shaft completely with out a load, I swapped a 4450 valve on to it and it didn't matter, on those it takes pressure to release it, a spring loaded brake, if I loosened the brake line it would stop, while slobbering oil out the loose line. I was thinking the bleed off was clogged a bit, not letting the pressure leak away to let the spring loaded brake engage,, the customer was not concerned with it so he put it back on a big manor spreader, it would not spin the spreader It would have had to be split twice to get to it, the second split would need the front of the cab supported, this was on a front MTWD/power shift.

 

[Craig C]

So are you saying the pto brake is spring applied and pressure release. And relieving the pressure that should have been static oil allowed the brake to stop the shaft.

 

[tim s]

Yes...

 

[jared in wi]

Craig,

I had the same problem on a customers 4650 once, his was a Powershift transmission.

The way the pto brake works is that it is spring applied and hydraulicly disengaged. While the tractor is running, a small amount of pressure oil is applied to the brake to allow it to rotate after the pto is disengaged with a load on, to prevent premature wear of the brake.

What I had happen is that the pto brake pressure going to the brake (when the pto was disengaged) was too high allowing the brake release and the pto to coast. There is a relief valve on the pto brake circuit to regulate the pressure. I ended up trimming the spring to bring the pressure down to allow the pto brake to apply more.

I would highly recommend getting the op and test manual for the 4650 tractor and it will go more indepth on it. Also, you can do this fix with out splitting the tractor.

Jared