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Ford 681 Select-O-Speed Questions


 
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Spencer P
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PostPosted: Thu Oct 04, 2012 1:56 pm    Post subject: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

I recently purchased a 681 SOS (year=1960). Am rebuilding the engine and the transmission looks good. I have the necessary manuals (even got the owner"s manual) but still have a couple of questions.

1)There is a lever on the left side and just forward of the seat (lower on the transmission casting) marked on and off. Anyone know what it turns on or off?

2) The pull handle on the dash...I"m assuming that if I pull it out I disengage the PTO and with it in the PTO runs...right? (if I"m wrong...what does it do?) I originally thought this was to shift it to the higher PTO speed, but I found another lever on the transmission housing that I think (maybe) does that.

Many thanks for your input.
 
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Larry NCKS
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PostPosted: Thu Oct 04, 2012 3:11 pm    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote


1) This lever shifts the PTO from engine driven to ground driven. The PTO is driven by the rear axle in the ON position.

2)You have this backwards. In is disengaged. Out is engaged. Most of these PTOs rotate even when disengaged when there's no load on them.

If you have an operators manual, the answers to both your questions are contained therein! Might be beneficial to spend some time studying it! Wink
 
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Spencer P
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PostPosted: Thu Oct 04, 2012 8:50 pm    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

Thanks for the info. I've poured over the owner's manual (at least what I have) and could find nothing...perhaps I overlooked something. That does clear up a few things. I'm a rank amateur when it comes to stuff like this. Once put together an old MG...but tractors are another animal all together.
 
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Sean in PA
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PostPosted: Fri Oct 05, 2012 3:43 am    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

Larry has it right.

There are 2 levers on the side.

The lever toward the front of the tractor is to switch between the 2 speeds that are driven by the transmission input shaft and the PTO speed on these only vary based on engine rpms. It should have 3 positions. One is for 540 rpm, middle is "off" the last is for 1000 rpm.

The lever toward the rear is for the "ground speed" PTO mode, which is driven off the output shaft of the transmission and therefore varies its speed based on how fast the rear wheels are turning.

The 540/1000 rpm mode and the ground speed mode are setup so that you should not be able to engage one while the other is already engaged. In order to be able to engage the ground speed, you must put the other lever in the middle, or "off" position. Likewise, in order to move the forward lever out of the "off" position to either the 540 or 1000 position you must first put the ground speed lever into the "disengaged" position.

These levers configure what is going to drive the PTO, and sets up the gearing going into the PTO clutch. The handle on the dash is what controls the engaging and disengaging of the PTO clutch itself. As Larry said, pushing the handle on the dash all the way in disengages the PTO clutch, and pulling it out engages it.
 
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Larry NCKS
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PostPosted: Fri Oct 05, 2012 5:20 am    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

Sean in PA wrote:
(quoted from post at 06:43:07 10/05/12) Larry has it right.

The 540/1000 rpm mode and the ground speed mode are setup so that you should not be able to engage one while the other is already engaged. In order to be able to engage the ground speed, you must put the other lever in the middle, or "off" position. Likewise, in order to move the forward lever out of the "off" position to either the 540 or 1000 position you must first put the ground speed lever into the "disengaged" position.

These levers configure what is going to drive the PTO, and sets up the gearing going into the PTO clutch. The handle on the dash is what controls the engaging and disengaging of the PTO clutch itself. As Larry said, pushing the handle on the dash all the way in disengages the PTO clutch, and pulling it out engages it.


This is not correct in my understanding, Sean. The position of the one lever has no bearing on the other. If the ground speed PTO is engaged by the rear lever, there is an interlock built in that should prevent the dash control from being pulled to the on position. The dash control has nothing at all to do with the ground speed operation of the PTO. It only engages the engine operated PTO clutch.
 
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Sean in PA
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PostPosted: Fri Oct 05, 2012 8:14 am    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

Larry, thanks for the clarification. My S-O-S is only the single speed PTO. I thought that the interlock was between the 2 levers. But between the the handle on the dash and the ground speed would work as well I guess if the handle on the dash isn't needed for the ground speed. So the PTO clutch isn't used for the ground speed either then?

What abut the large number of S-O-S tractors where the handle on the dash doesn't actually shut off the PTO properly when you push it in? Can the PTO shaft be connected to both the ground speed gear and the input shaft gear at the same time, and can't that cause damage?
 
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Larry NCKS
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PostPosted: Fri Oct 05, 2012 11:34 am    Post subject: Re: Ford 681 Select-O-Speed Questions Reply to specific post Reply with quote

Sean in PA wrote:
(quoted from post at 11:14:34 10/05/12) Larry, thanks for the clarification. My S-O-S is only the single speed PTO. I thought that the interlock was between the 2 levers. But between the the handle on the dash and the ground speed would work as well I guess if the handle on the dash isn't needed for the ground speed. So the PTO clutch isn't used for the ground speed either then?

What abut the large number of S-O-S tractors where the handle on the dash doesn't actually shut off the PTO properly when you push it in? Can the PTO shaft be connected to both the ground speed gear and the input shaft gear at the same time, and can't that cause damage?


The PTO clutch is not used for ground speed. It is used for engine speed only. Since it is not engaged and really has no drving force, even thogh the PTO does tend to rotate under no load, there will be no damage to components for having the ground speed engaged.
 
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