PTO's

with being a fitter/driver i know how pto’s r driven an operate etc but it got me thinking the other day, how do you engage a pto with a fully automatic gearbox ?

as with a manual box, u dip the clutch, flick the pto into the engage postion and release the clutch an bingo, but how would you do it without a clutch, without just flicking it up and hearin a crunch from the gearbox ■■

mark h:
with being a fitter/driver i know how pto’s r driven an operate etc but it got me thinking the other day, how do you engage a pto with a fully automatic gearbox ?

as with a manual box, u dip the clutch, flick the pto into the engage postion and release the clutch an bingo, but how would you do it without a clutch, without just flicking it up and hearin a crunch from the gearbox ■■

it doesn’t crunch mate, all the automatic volvo’s at van den bosch all have pto’s, engines running, flick the switch, and its a smooth changeover

We run 4 105xf with AS-Tronic boxes and a Scania Opticruise all the Daf have twin pto"s 3 for blowers and tippers seperate ptos for each and 1 with walking floor and tipper again seperate ptos.All you do flick the switches like diff-lock lock switches wait a couple off seconds and they working no crunching or noises

They crunch only if you don’t do while the engine is idle.

If you did it carefull with the old PTO’s you could do it also without the clutch.

The I-shift is a manual box, electronic operated, if you switch the PTO in before he is idle you hear them grind.
There is a problem if you have a heavy silocompressor and he cannot start up at freewheel (if you have back pressure) he will give a kind of a bang not so nice.

Most road vehicle PTO’s I’ve come accross over the past 15 years or so (mostly slide back recovery trucks) have had auto-engage.

IIRC the switch is just electric to operate a solenoid which moves the gear into position. Most refuse to engage if the gearbox is not in neutral. (hmmm, how do grit spreaders go on then?)

Driveroneuk:
Most road vehicle PTO’s I’ve come accross over the past 15 years or so (mostly slide back recovery trucks) have had auto-engage.

IIRC the switch is just electric to operate a solenoid which moves the gear into position. Most refuse to engage if the gearbox is not in neutral. (hmmm, how do grit spreaders go on then?)
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You can have PTO driven by the distribution gears of the valve train, constant engaged, VdB has TRS generators on certain trucks for the cooling motors of reefer conttaines (400V) the hydraulic pump to drive them is built to the front of the engine.
If I remember it right a lot of Dutch garbage collect vehicles have the hydraulics constanly driven by the engine, so the position of the gearbox doesn’t affect them.
If you ever drove away with the PTO engaged on the gearbox you know what I mean.

See if you pull away and them slan on the brakes just as the ishift box is about to change gear, you get a lovely grind from it lol :laughing:

Just ask for an Allison workshop manual and parts catalogue.They’ve been putting PTO’s on Auto boxes used in fire trucks for years.

From what I remember from working at Turners in Glasgow and I assume you mean an Allison gearbox.
There are mountings on the gear box to have a PTO mounted after the torque convertor but before the gear bands.

I drove a Scania 86 (Rigid) with a hooklift and A frame trailer, to engage the PTO you pressed the clutch pressed the button and put the truck into 8th gear and let the clutch out. It worked but it was a worrying experience the first time I used it, especially as you pull the skips on with the handbrake off! :stuck_out_tongue:

On the old F10 and F12 at VdB we controlled the PTO for the silo compressors and tank compressors from the outside.
Had 3 buttons on the outside 1 for the clutch, 1 to engage the PTO, 1 to operate the accelerator.
You got very handy with them, flick the clutch, wait 30 seconds, flick the PTO and release the clutch slowly, when engaged flick the accelerator who would bring the revs up to 1000 revs.
When somebody was smart in the morning the would flick the clutch switch and you would wake up with you clutch pedal pressed to the floor. :grimacing: :grimacing: :grimacing:
Or they operated the accelerator and you would wake the whole parking up because the engine would start at 1000revs. :blush: :blush:

PTO’s are like Marmite, you love them or hate them :unamused: :unamused:

yer i mean u can hear the pto engage when you dont use the clutch, is it just the exact same with an auto then ? as some1 mentioned about opticruise in the scania’s they still have the clutch pedal as thats what we run, i was always told to dip the clutch when engaging the pto thats all !

My Merc is auto Mark and once the handbrke is on you just press a button on the dash,takes about 5 seconds before it engages doesnt grind but you can actually hear the truck clutching smoothly. If you try to drive the pump will stay on but your rpm is limited to about 1000 .
I wonder if driving with the pto on(just around a yard loading) would cause the clutch servo to expire as mine has recently done :blush:

Carryfast:
Just ask for an Allison workshop manual and parts catalogue.They’ve been putting PTO’s on Auto boxes used in fire trucks for years.

I used to drive a Foden tipper with an Allison auto box, PTO was simply engaged by a leccy switch on the dash, when the big red light was on you could pull the lever to tip, it even worked when you were driving along as well :blush: :blush: :blush:

brados:

Carryfast:
Just ask for an Allison workshop manual and parts catalogue.They’ve been putting PTO’s on Auto boxes used in fire trucks for years.

I used to drive a Foden tipper with an Allison auto box, PTO was simply engaged by a leccy switch on the dash, when the big red light was on you could pull the lever to tip, it even worked when you were driving along as well :blush: :blush: :blush:

Just like the ones on those fire trucks which I used to drive. :wink: :laughing:

i used to drive a daf 95 410 with an auto box, usually just stuck it in neutral then switched the pto on, you could still move with it in gear but you were lucky if it was more than walking pace with the dash going crasy telling you the pto was still on. the autos never really suited landfill sites though.

i prefered my old twin split foden for that work. worked a treat

PTOs on Auto boxes have an internal clutch pack that is operated by a solenoid to engage.

On things like refuse trucks the pto will be permanently engaged and the hydraulic flow dumped to tank when the hydraulics are not required.

Some cement mixers have a front mounted PTO to drive the drum whilst moving

On Pto for Allison Auto there are 2 types

Constant Mesh - allways running. Hydraulic System dumps flow to Tank via electric operated valve, Switch in cab can switch hydraulics on/off

Or Hotshift - This type of PTO has an internal clutch between PTO output and the drive gear. Clutch is opperated by an electric solenod valve which give the internal clutch pressure to engage.

On our MAN TGAs you cant engage the PTO unless in Neutral and handbrake on, then you cant put the vehicle in gear until the PTO is disengaged.

bit of a PITA when youre trying to tip in a farm shed and have to move forward and tip higher at the same time. You have to keep putting handbrake on to lift the body.