John Deere 6405, losing power at PTO

[flybikedave]

My PTO is turning an 8' flail mower and while the engine is running great, suddenly when under a load the PTO just slows to a halt. The flail mower does not seem to be the problem as once I stop the engine and raise the mower, I can turn the PTO shaft by hand and rotate the 8' flail mower. I checked to make certain the PTO switch remains engaged and locked, but RPM's just slow to a halt once a load is applied. I then disengage the PTO, raise the mower and re-engage the PTO and it comes back up to speed, only to stop again when I lower the mower into the grass. Doesn't look good. Any tips, suggestions or ideas would be greatly appreciated. Dave

 

[flybikedave]

Been searching the web for answers and will look at: PTO switch, PTO solonoid, seat sensor, RPM sensor. Guess I'll try jumping the switch, bypassing the seat sensor and checking for power at PTO solonoid, UNLESS some kind soul steers me in another direction. Thanks in advance.

 

[Zebrafive]

Your PTO speed sensor is the same as your ground speed sensor. You could swap them and see if your speedometer still works OK. Part number for both is AL204621.
I lost the speed read out on my 6415 and swapped these two sensors. That fixed my speedometer. New sensor was about $20 at the JD dealer. O-ring was another $2.

 

[jd110]

If pto stays running ok when not under load, I suspect you have a low pressure problem. Do you have a gauge to check pto clutch pressure? If not, then pull the pto solenoid and look for blown orings. Also the rectangular housing that the pto solenoid is mounted in can be removed and check for a plugged oil passage. There are some small holes that can get plugged with a sliver of oring from somwhere and cause low pressure. You also could have a failed pto clutch which would require removal of entire rear pto housing. If you can check pressure, look for about 240 psi when pto is engaged.

 

[flybikedave]

Thanks JD110. Do I check pressure at the port on the rectangular housing marked "clutch"? And, if I get about 240 PSI, than I suppose that's really bad news in that clutch is failing, right? I ran it again under a light load (thin grass) and it kept up RPM OK, but then my previous fuel problem reoccurred and shut me down. You will recall, I cleaned the badly blocked pick up screen and thought I had it, but I believe it is perhaps the electric fuel lift pump in the tank that fails after 20 minutes or so. Will try an auxillary pump with separate line for testing purposes and if it keeps running will then change the in tank pump. THEN, maybe I can get back to the PTO problem. I REALLY appreciate your input. Thanks, David

 

[jd110]

That is correct. check pressure at clutch port and if pressure is good, the clutch is bad.

 

[flybikedave]

Thanks again jd110. Obviously you don't know me, but I've rebuilt a Farmall Cub engine, several 4 cyl. outboard engines, 2 aircraft engines, and currently maintain my 4 tractors, 2 trackhoes, a dozer and dump truck, BUT have never torn into such a large PTO. Just wondering if I can handle swapping out the clutch, because there are no such repair facilities nearby and it is a big task to remove the 2 side boom 8' hydraulic flail mowers and its a heavy load to transport it with them attached. Would the $159 tech. manual be of much assistance to me?

 

[Tx Jim]

If the newer tech manuals are as informative as the older JD TM then it should contain very valuable info.

 

[flybikedave]

I've now checked pressure at PTO clutch and PTO brake test ports. Both indicate 180 lbs when PTO is engaged and disengaged (clutch & brake). Was hoping for 240-250 lbs. I pulled PTO solenoid to inspect O rings and operation, both looked good. Solonoid only moves about 1/8 to 3/16", but I think that might be full range. Question: Is 180 lbs enough to keep PTO clutch engaged under heavy load, or could that be the cause of my clutch slippage? Might it do any good to pull modulator valve and look for trash? I found a used modulator valve and PTO clutch assembly at Wenger's for $80 & $210, but don't know if I should proceed in that direction. Any input would be greatly appreciated.

 

[jd110]

I went and looked at the manual. I was off on my pressure spec. It calls for 165-185 psi so what you have is good. I was thinking of newer model specs. I would recommend keeping the gauge in while you are running the mower and see if the pressure drops when the pto slows down. If pressure stays good then the clutch is bad. One other thought. Do you have swappable 540/1000 rpm pto? If so, it is possible you have a gear problem.