Chev CMP PTO design and use
 

Hello Gentlemen!

I’m Adam, from Australia, and I’ve been reading the forums for quite some time now.

I am thoroughly committed to buying a Chev C60L, when I’m fortunate enough to find one.

I have questions about the PTOs on these vehicles, and hope I’ll find some advice from you clever chaps.

I used to have a ‘73 F350, with a PTO driving a hydraulic pump.
It ran a loader crane, and although useful, it was quite noisy.

I’d like to use the PTO on the CMP to power a hydraulic pump, to run a small crane, water pump, compressor and generator.

What is the the range of operating revs for the PTO’s on CMPs?

Are the PTO gearboxes of straight cut or helical gearing?

What sort of horsepower can be transmitted through the PTO?

Are these PTO gearboxes suited to intermittent use, or continuous duty?

Are these noisy units, or can they be tweaked for quiet operation?

It’s possible that I’d use the compressor, pump or generator, for stints of half an hour.
Is this too much of a demand on these PTO gearbox units?

Looking most forward to any advice!

Thanks very much, fellas.
- Adam

You might be surprised to learn that there are not one, but 2 PTO outlets on a C60L (or any other 4x4 CMP).

The common one is a standard 6 bolt SAE PTO on the side of the gearbox (LHS on a Chev, RHS on a Ford). This was typically not used to power shaft operated implements or hydraulics, but was used for a tyre pump. The gears in both the Chev and Ford 4 speed boxes are straight cut gears. PTO manufacturers like Chelsea make various shaft drive units (W/ or W/O speed reduction or overdrive) or hydraulic drive units, but the majority of the second hand ones you will come across are for the helical gears typically found in a Ford/Dodge NP435 or Chev SM420/465 gearboxes. You might be able to order replacement straight gears for them from Chelsea, but then again you might just be forced to order a brand new unit with straight gears complete. BTW, The Australian Army DID use a Servex-brand Hydraulic PTO unit on the C60S tippers, but you're not likely to stumble across one of those in a hurry.

These gearbox PTO units were usually only driven at around 800 engine rpm, not because of a speed limitation of the PTO or torque limit on the gears, but because of the design limits of the tyre pump. Excessive revs would increase the piston speed causing the pump to overheat and seize. The noise from the PTO is practically indistinguishable from the straight gearbox, so yes! Noisy!!

The other PTO fitted to CMP trucks was a larger unit to drive the winch, and was bolted on to the rear of the transfer case. These were only a dog clutch flange output to a universal jointed shaft to the chassis mounted winch. Although only a single speed, the output rpms could be varied by engine speed and gearbox gear selection. The PTO is capable of being operated at any rpm speed or gear, as it is lubricated by the T/Case gear oil (although naturally, winching was done at slower controlled speeds). As this unit is a flange output design, your hydraulic pump would need to be remotely mounted. Heck, if you were imaginative enough, you could fabricate a 3PL off the rear of the chassis and shaft-drive implements on the move. It's certainly been done before with farmer-ised Blitzes in the past! :kangaroo

There was another PTO, albeit from a 15cwt. The chev 15cwts had a PTO on the transmission for driving the water pump on the water trucks. I'm not sure if any of the larger tank trucks used this PTO, or simply the one off the back of the transfer. case.

We used to pick up those transfer case mounted PTOs from Princess Auto in Winnipeg. I still have one somewhere wrapped in preservative...I think they cost $5.

For the image of the PTO of the 15 cwt truck's water pump, see post #17 of http://www.mapleleafup.net/forums/sh...535#post249535

Interesting discovery recently
 

Hi

One thing to consider or take into consideration when using the PTO on the transfer.

Recently while working on my 1941 C60L I had it up on jack stands I put the transfer case in NEUTRAL and discovered that front axle was engaged and hence locked to turn with rear wheels. I also noticed this when using the winch which is connected to the transfer case PTO.

Now this is a useful feature when using the winch because it means the parking brake is applied to all wheels, when pulling an object. But means when you are wincing the vehicle itself you can use only the pulling power of the winch with no help from wheel power.

But might not be so useful to have 4x4 engaged if you were using the PTO to drive a hydraulic pump. This of course was sorted out in shift linkages or by adding another lever.

Cheers Phil

Thank you, Gentlemen!

Your responses are greatly appreciated, and have given me much to think about.

I’m indebted to you all.

- Adam