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Daniel Wilson
Daniel Wilson,
Category: Transmissions
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Experience:  Owner at DJ Wilson
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I have a 2009 mack gu813 dump truck with a 4500 allison in

Customer Question

I have a 2009 mack gu813 dump truck with a 4500 allison in it. We gust a new pto on it and the pto will kick on and work fine as long as u don't drive very far and get the transmission temperature up then once that happens the PTO doesn't work anymore until the temperature drops back down then it works finetrying to figure out if there is a sensor that would be causing that or if the coolant level being low might be causing that
Submitted: 1 year ago.
Category: Transmissions
Expert:  Daniel Wilson replied 1 year ago.

Hi Mike, My name is***** will be glad to help. I want to be sure I am understanding you correctly. Are you driving the truck with the PTO still engaged? The PTO should only be engaged when running the pump to dump the body. Are the hydraulics not lifting the body when this happens? If so it could be a pump problem rather than the PTO. Slide the pump out of the PTO and see if the PTO is turning. Let me know

Customer: replied 1 year ago.
No I only in gadgets it while sitting still. It will work just driving around my lot with no problems. Then when I drive it down the road about 15 miles it won't work. Then if u let it sit for a couple hours and try it again it will work again till u drive it a little distance then the same thing all over again. Didn't know if there is a sencer I need to be looking for on the coolent side of the transmission or the fluid side of the transmission.
Customer: replied 1 year ago.
It's an electric pto and it's like there is a relay or something that is kicking out like it's hot. And not letting power get to the pto to Kick everything in
Customer: replied 1 year ago.
I just tried the pto again and it came on so I drove the truck and kept stopping and trying it as the transmission temperature went up and it worked till it got up to 180 degree then it stopped working. So I'm wondering of its has something to do with a thermostat for the transmission or something
Expert:  Daniel Wilson replied 1 year ago.

Are you getting any fault codes? What make and model PTO is installed? Click here to access the transmission troubleshooting information. Let me know the PTO information you have.

Transmission Troubleshooting

Expert:  Daniel Wilson replied 1 year ago.

If a PTO is present, it will be mounted on either the left side or the right side for

a 3000 MH transmission depending upon the converter housing con


guration. The

PTO is located on the left side or top for a 4000 MH Series transmission. The

PTO drive gear is engine-driven and therefore provides direct engine power. The

PTO can be operated when the vehicle is either moving or stopped.

The PTO gear is in constant mesh with the drive gear in the converter housing.

PTOs are either constant drive (output always powered) or clutched drive. The

output of a clutched drive PTO is powered when the PTO clutch is pressurized.

Be sure that the limits for PTO engagement speed and operational speed are not

exceeded. Consult the vehicle manufacturer’s literature for these speed limits.

Also, all Motorhome Series-equipped vehicles with PTO enable have engagement

and operational speed limits programmed into the ECU to help protect PTO

equipment. Some speed limits have default values which are programmed out of

the operating range and will need to be set for your particular PTO duty cycle.

Consult your vehicle manufacturer to see if your transmission has been

programmed and what operational limits have been established.

When the programmed engagement speed is exceeded, the PTO will not engage.

The PTO engagement must be retried after the speed has been reduced. When

operational speeds (either engine or transmission output) are exceeded, the PTO

will deactivate and the PTO engagement process must be repeated.

Expert:  Daniel Wilson replied 1 year ago.

Have the Allison diagnostic software plugged in to check and possible reset the parameters in the TCU as it sounds like it is programmed to shut down under the circumstances and try reprogramming and updating the software to see if it resolves your problem if no fault codes are present indicating another problem. Let me know

Customer: replied 1 year ago.
It is a 4000. Pto mounts on top. No falt codes. It works fine till the transmission temperature gets up to 180 degree then the pto won't turn on til u let it set till it gets back down to about 150 the it works again.
Expert:  Daniel Wilson replied 1 year ago.

Thanks for the update Since there are no codes the only thing you can do is check for signs of PTO failure by checking for metal/debris indicating internal problems and if okay you will then need the Allison diagnostic software connected to read live data and check the current PTO settings and a possible software update and reflash. If there were fault codes it would be easier to pinpoint a problem area. If there are no signs of failure in the oil and filter have it plugged in for further diagnosis. Let me know

Expert:  Daniel Wilson replied 1 year ago.

Hi Mike, Did you get this resolved? Please take a moment to rate my service as that is how the site credits the experts for their time helping on the site.