TN75 and other TNs - PTO drag?

yeehaw · May 5, 2010

have a TN75 that the PTO works fine - starts up "slow" as long as I engage it slow-- fast if i throw it in gear - which i dont do. works fine bushhogging 17-1800 rpm--- yet when you turn the PTO off-- even when the tractor is idled down to 1000 or so, the sucker keeps spinning like crazy - as if there is no drag/friction at all to it. Will do it even if you shut the tractor off. I have started lowered the bushhog all the way to the ground to stop the PTO from spinning in excess b/c of this. Is this normal for these TN's and if not what is going out? Tractor is an 03 with only about 1000 hrs.
I've been around all sorts of tractors from 20hp up to 100+ and none of them have ever done anything like this before....
thanks

DocHeb · May 5, 2010

Does your bushhog have an over-run clutch on its PTO shaft?

My 2002 TC40D has a very strong PTO brake that prevents any movement after a second or so, but I have no direct knowledge of the TN series. I suspect yours should have a PTO brake. Someone that actually knows what they are talking about will chime in...

flyingcow · May 5, 2010

I've only snowblowed with mine. Just got the tractor in Feb. When i shut my pto down it stops as it should. Got very little drag on the blower. Can turn it by hand when hooked up to tractor. Won't be bush hogging until another month or so. But i suspect it will work as it should. My older tractors would keep turning. But I had other issues also.

Does you 3point stay level when at an idle? Does it immediatly drop once tractor is shut off?

If you don't get an answer soon, try posting this on the general forum.

yeehaw · May 5, 2010

Everything stays level---works good--hydraulics are good---

not sure what an "over-run" clutch on the pto shaft is--- just have a typical bushhog that has a slip clutch instead of shear pin...

have seen it also spin freely without anything hooked up...
may post in general tonight if not a lot of hits
thanks

DocHeb · May 5, 2010

yeehaw said:
not sure what an "over-run" clutch on the pto shaft is--- just have a typical bushhog that has a slip clutch instead of shear pin...

An overrun clutch (well described in this thread) lets the driver turn off the PTO but lets the implement keep spinning until friction finally wins and it stops. This is useful for tractors that might allow the momentum of the heavy implement transmit through the PTO and drive the tractor forward. The question is: "does your TN have a PTO brake or a built in overrun clutch?"

barbqranch · May 5, 2010

On my TC29D, the shaft keeps spinning for quite a while. Also, with the engine shut off, I can freely turn the shaft. The brush hog is a huge flywheel, holding a lot of energy when spinning. When you shut off the tractor engine or disengage the PTO, that energy has to go somewhere. Far better to let friction slowly dump it, rather than quickly using it to possibly bust something in the tractor. I'm just real careful to not get too close till it stops spinning!

flyingcow · May 5, 2010

I'm quite certain there is no pto brake on tractors this size. The pto should disengage and the implement will spin for a short time until the energy is gone. And, if operating properly, the pto will not spin when not hooked up to anything. But, yours is still spinning, not at full rpms, but it will still spin, like it's partially engaged. Irritating to say the least. Sorry, no help, been there with other tractors.

SPYDERLK · May 5, 2010

yeehaw said:
have a TN75 that the PTO works fine - starts up "slow" as long as I engage it slow-- fast if i throw it in gear - which i dont do. works fine bushhogging 17-1800 rpm--- yet when you turn the PTO off-- even when the tractor is idled down to 1000 or so, the sucker keeps spinning like crazy - as if there is no drag/friction at all to it. Will do it even if you shut the tractor off. I have started lowered the bushhog all the way to the ground to stop the PTO from spinning in excess b/c of this. Is this normal for these TN's and if not what is going out? Tractor is an 03 with only about 1000 hrs.
I've been around all sorts of tractors from 20hp up to 100+ and none of them have ever done anything like this before....
thanks

Sounds like its just coasting down. Does the output shaft stop quick if theres no implement? If so jts normal according to all 4 of my non tiny tractors. The BX has a pto brake. Wish it didnt. Just something else to go wrong.
larry

yeehaw · May 5, 2010

SPYDERLK said:
Sounds like its just coasting down. Does the output shaft stop quick if theres no implement? If so jts normal according to all 4 of my non tiny tractors. larry

Short answer - no

Long answer --- the shaft is very easy to turn by hand when unattached when the tractor is both off and running. Very surprised by the running as most shafts you can barely budge (or not move at all) when they are running and then you have to put a little oomph into them in order to turn them when the tractor is off--- to turn to match up with the implement's shaft/yoke...

I thought a little bit more about this and we used to have an older massey 383 that was kinda like this as the batwings would never slow down after the PTO was disengaged --- so maybe it is normal---just seems odd.

do have another question that will post separately
thanks for all the replies and any additional info will be greatly appreciated