3910 brutal PTO engagement

[duncan_hardy]

I have a problem engaging the PTO on my 3910. I always get a huge bang as the drive connects and shock loads are transmitted through to the implement.

According to my I&T shop manual there are two types of PTO fitted to my tractor, either independent (in which the PTO is engaged by a dedicated hydraulic PTO clutch) or transmission (in which the PTO is engaged by a splined sleeve on the gearbox shaft ie after the main clutch). Judging by the pictures in the manual, I have the transmission type PTO.

Now, when I engage the PTO with the engine running, there is this dreadful bang. Again, according to the manual, the transmission type PTO is driven off the gearbox input shaft. So the drive should come after the clutch. However if I press the clutch it makes no difference. The clutch is perfectly effective at preventing drive to the wheels (no creep when in gear) but it doesn't seem to disconnect the PTO. Even if I depress the clutch fully for 5 secs, when I engage the PTO there is a huge bang and the drive is carried through to the implement.

I don't understand this. Is the manual wrong? Is my transmission system defective? Or were some models built with a permanently driven PTO input shaft (like an independent PTO) but with a transmission type engagement?

Duncan

 

[JC-jetro]

However if I press the clutch it makes no difference. The clutch is perfectly effective at preventing drive to the wheels (no creep when in gear) but it doesn't seem to disconnect the PTO. Even if I depress the clutch fully for 5 secs, when I engage the PTO there is a huge bang and the drive is carried through to the implement.

I don't understand this. Is the manual wrong? Is my transmission system defective? Or were some models built with a permanently driven PTO input shaft (like an independent PTO) but with a transmission type engagement?

Duncan

Duncan,

Welcome to Blue Forum, What I marked in red does not make sense. In transmission driven pto there is only one "input shaft", You clutch all the way and input shaft to transmission should slow down to stop. I'm just thinking out loud here but maybe your clutch need adjustment where pushing the clutch pedal all the way does not seprate clutch disk from flywheel and the pressure plate completely to the point the friction is caused is enough to to spin the drive shaft and you have the gear in "neutral" hence not forcing the tractor to move forward. I know you did not say the gear in "neutral" when you engage pto.

At what rpm do you engage the pto?

I have transmission drive PTO on my 1700 and in order to avoid grinding I rev the engine down, clutch all the way and wait a couple of seconds to dissipate the input shaft rotation and any forward motion before engaging the pto and have had very little problem.

 

[RickB]

Forget the clutch pedal; you have independent PTO. They are a little harsh. Set the engine RPM's high enough to start the PTO without stalling the tractor, not much more. Learn to feather the PTO control gently. It can be done, and the PTO will engage quite a bit smoother with a little practice.

 

[JC-jetro]

Independent (hydraulic or electro mechanical) pto and Live pto (dual clutch) terms are used at times interchangeability from manufacturer to manufacture. If you have a wet clutch pack for pto coupling, then feathering is the way to do it. If you have dual clutch and pressing the clutch pedal all the way does not release the pto shaft and you will still grind when you engage the pto. The latter will require pedal adjustment. If you had transmission driven PTO as you mentioned my first post would be valid.

JC,

 

[jinman]

Let me restate what RickB said, "Learn to feather the PTO control gently."

If I don't feather the control on my tractor, I will pop a shearbolt on the cutter every time I engage it. As a matter of fact, I have memorized exactly where my lever starts to engage the PTO when the tractor is cold and when it is warm (There is a difference on mine.). I reduce engine rpm and push the lever fairly fast until I get near the engagement zone where I slow the engagement until I hear the mower start to spin up. Then, I go ahead with full engagement and raise engine rpm up to operating range.

When you disengage the PTO, lower your engine rpm again before disengaging the PTO. Even if your tractor has built-in overrun, this won't hurt anything. If it has a PTO brake, you'll extend the life of the brake/clutch by operating this way.

Good luck with your 3910. I've always liked that model of tractor.

 

[Hooked_on_HP]

JC
My 1900 has a dual clutch and 2 input shafts. One is inside the other. When I am mowing and start to bog the engine I push the clutch in half way to stop the motion of the tractor the mower keeeps running. If I push the clutch in all the way every thing stops.

 

[JC-jetro]

JC
My 1900 has a dual clutch and 2 input shafts. One is inside the other. When I am mowing and start to bog the engine I push the clutch in half way to stop the motion of the tractor the mower keeeps running. If I push the clutch in all the way every thing stops.

Right Bill, it is an option on 1700 as well that I do not have. What I was trying to get across was , like in your case (not all inclusive) when you push the pedal all the way disengaging the transmission first and then disengaging pto second, If you can not fully disengage the pto shaft clutch from the engine then upon PTO engagement you'll end up grinding the what ever type coupler you have between PTO input and output shaft.

JC,

 

[CCWKen]

My 3910 has the independent PTO. This means the clutch pedal has no bearing on the operation of the PTO. You might be getting "clunks" from too much wear or gear clearance in the driven line. I get it on my rotary mower but it's got a lot of wear. Just engage the PTO at idle then throttle up.

I think the PTO engagement lever is either on or off. I've never been able to feather the engagement on mine. And, you shouldn't be running shear pins on equipment over about 30hp anyway. Use a slip-clutch.

 

[duncan_hardy]

There's obviously some confusion here because of terminology.
To be clear...I definitely do not have a multiplate clutch separating the PTO from the transmission. There is a sleeve gear that engages the PTO with the transmission. It is either 'in' or 'out'. You cannot feather it. I also do not have a two stage clutch. As far as I know this has never been an option on the 3910.

I think JC-jetro has the right idea. It is a transmission PTO. However, according to the manual, if drive to the transmission is disconnected via the main (foot operated) clutch it should also disconnect the PTO. This doesn't appear to be happening. If I depress the clutch and put the transmission in gear with tractor stationary then the transmission is stopped. This must be the case because the rear wheels aren't moving. So the clutch is slipping as it should, the transmission is stopped, yet the PTO is still being driven. I can drop a brush cutter into long grass like this and the PTO doesn't even slow down. It beats me....

 

[tallyho8]

Your 3910 should have the same independent, hydraulically operated, pto that my 4610 had. You can not stop this pto by pushing the clutch down. The only way to stop it is to disengage the pto or kill the motor. You should always idle your engine down before engaging or disengaging your pto and then you should slowly move the lever into gear.

My pto engagement was very abrupt the short time I had my 4610 until one day when it no longer started when I pulled the lever. I was told that the hole in the pto clutch plates had stripped out and the tractor had to be broken down to repair with estimates of $2000 to $4000 so I sold the tractor.