so i was looking through some old ford sales brochures and i noticed something about an optional power take-off provision, standard on stickshift, optional with 7.3 and 6.8 auto.

i'm guessing this could drive a generator or spin something? what is it exactly?

 

PTO its for trucks that might have a commericial use or for fire dept purposes. The PTO could be used to run a winch, or for the FD a small fire pump. Its driven off the trans. Some setups you can still drive but most are not set up that way.

 

There's a standard interface (a couple of different sizes, actually) to connect an auxillary power output to a transmission. Smaller trucks would use this to drive a hydraulic pump for a dump hoist or a winch. Larger trucks will use these for all sorts of things, but hydraulic pumps for loading/unloading various types of cargo are the most common thing I've seen. Also, larger transmission will have two, three or more of these provisions on each transmission.

The actual interface to the transmission is a six or eight bolt rectangular opening on the side of the transmission housing that a smaller housing with a spur gear and collar clutch bolts onto. THe spur gear engages a gear in the transmission and by engaging the clutch in the PTO box and letting the normal clutch out you get the output shaft to spin. I think automatic transmission can have PTO provisions too, but I make a point of ignoring anything automatic.

Now days on smaller applications like winches and dump bodies on one ton trucks it's more common to have electric power. I don't care for electric because the duty cycle is much lower but it's easier to install and you avoid some problems, like getting things wrapped up in the little auxiliary drive shafts (that was a bad day...).

I hope this helps!

 

You beat me to it, DAFBFD58! There's no reason you can't drive with the PTO engaged, indeed some equipment requires this to be useful. You're thinking of the larger firefighting apparatus where the pump is not a true PTO - the drive coming out of the transmission is actually disconnected from the axle(s) to drive the pump.

I once saw drilling apparatus which used a medium duty truck transmission to regulate the drill speed - the output of the transmission drive the drill but the power got in through a PTO box driven by a hydraulic motor!

 

The PTO on the 4R100 transmission would not operate when the truck was driving. It was changed for the TorqShift trans so that the PTO can operate when the truck is driving.

 

Mark: very interesting. Not to hijack the thread, but now I'm curious! On the automatic, mechanically why can't you put the transmission in gear when the PTO is engaged (do you do something like lock the TC up when the PTO is in?)? Also, how do you stop the gear that the PTO box meshes with to engage the PTO clutch (ie: there's no clutch for the transmission, so how do you stop the assembly from turning)? I know you can engage some PTO boxes without putting the clutch in if the engine idles really slowly, but I always though this was not a good thing to do.

 

Tp engage the PTO on an automatic you engage the PTO with the vehicle in gear - vehicle is stopped of course.

 

What usuially happens is a gear will move when a switch or something tells this certain gear to move to a position that will connect with the pto system not the drive gears. Unless the transmission is designed to do both you can only use the pto or drive, not both.
And for your comment to me, there is no reason why you can't do it. I said most times you can't. Most full size fire trucks have pumps that are driven off a small drive shaft that is connected to a PTO box that is mounted to the side or top of the trans. When we engage the pump, the PTO is then powered by the trans but the final output is not going to the drive wheels but its moved to the PTO. I have seen every type of truck out there. From brush to massive crash trucks. I am a military fire fighter and I have driven them all. Few trucks are designed to have the ability to "pump and roll". Most are crash trucks but there are a few brush trucks and a couple tankers I have driven that are set up so that you can move while spraying water. It all depends on hom you design the truck and what capibilities you want out of it.

 

I'm not sure on the 4R100. I never studied how the PTO worked on that trans. I think they used a combination of clutches to power it that precludes driving the truck.

To disengage it the PCM disengages the clutch that is powering the PTO. Automatics have clutches, just no clutch pedals.

 

I was under the impresson that, on the PTO on the 6-speed, the PTO gear turns any time the engine clutch is engaged. The gears will always stay meshed, but, like a belt driven A/C compressor, there can be a separate clutch to engage the gear to the shaft on whatever you are trying to power (generator, air compressor, hydraulic pump...)

If not, I guess I'll just search for a belt diven compressor for a 5.4L SD

 

If you look on the Chelsea PTO site there should be lots of info. Back in the days when I was installing PTO's on trucks the instructions were to do just that with an automatic - put it in gear - engage the PTO - then put it in neutral. This would allow the engaging of the PTO gear with the transmission gears stopped - of course this was to be done with the truck stopped.

 

I know on an 05 Auto trans tow truck i have done some work on, the PTO will work any time, it is a constant mesh gear but the switch that activates the clutch on the pto also hooks in to the PCM which raises the idle and locks the TC. When the brake is pressed or the truck gets put in gear you loose the high idle and the TC lockup. This is the PCM wire that most use for high idle mod, The pto wire or charge protect wire. Not sure how the pto would work with out the TC lockup. I know our 95 truck with a stick you could use the pto and drive but if you ran the rpm's too high you would blow the relief valve on the hyd system.

 

So how does one determine if his 4R100 trans has the PTO provision or not- does anyone have a pic of what to look for?

 

i started quite an informative thread. i just wanted to know if i could use it to power a blender so i could make margaritas.
i really was curious, not trying to be funny/jackass.

 

it seems that BOSS has a direct mount air compressor for the Automatic, but it apparently doesn't work on the standard...probably the difference between gear oil and ATF...