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Allison MT 653 pto issue on 94 F700 dump

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Allison MT 653 pto issue on 94 F700 dump

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Old 08-01-2018, 12:20 AM
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Allison MT 653 pto issue on 94 F700 dump

Last fall I had intermittent issues getting dump box to lift. My mechanic traced it back to pto gear not turning the pump. My question is how is the pto gear set up? Zero metal shavings or debris was in the fluid or magnet in the pan and the intermittent operation before it quit completely has me baffled. It seemed to work after fluid got heated up before it quit entirely but that may be circumstantial. I hate to give up on the truck if it's an inexpensive fix. It was a municipal truck and only has 35,000 miles on it but probably a lot of dump cycles for background info on the truck. Drives and shifts perfectly but zero fluid being pushed through hydraulic pump when pto is engaged.
 
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Old 08-01-2018, 04:49 AM
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Need to know the make of the PTO is it cable or air operated. Pretty simple a sliding gear slides & meshes with the trans counter shaft. If the PTO drive shaft is turning then its a pump problem. I'm not understanding the
"seems to work after fluid gets heated up" The system does not work hard enough to get heated.
 
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Old 08-01-2018, 09:36 AM
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Originally Posted by big job View Post
Need to know the make of the PTO is it cable or air operated. Pretty simple a sliding gear slides & meshes with the trans counter shaft. If the PTO drive shaft is turning then its a pump problem. I'm not understanding the
"seems to work after fluid gets heated up" The system does not work hard enough to get heated.
First it's not an air pto. I have a **** on cab floor to lift to engage. The part about fluid heating up was more a question of are there clutches that engage the pto gear. Last fall when problem started I could get the dump body to rise partially and then it would stop. If I dropped it and tried again I could get it to raise higher the second time and it might take 10-12 cycles like that to get dump all the way up. Then after sitting for a month in October it would no longer raise at all. In the spring when I got my mechanic to look it over he said pump is fine pto gear won't turn the pump. If it's a mechanical issue, why was I able to work it some and then it quit entirely. All the fluid, hydraulic and transmission, was clean with no metal pieces or shavings. So I'm trying to sort out what the issue could be without spending a ton of money on what amounts to a couple thousand dollar rusty old dump truck that I use on my farm.
 
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Old 08-01-2018, 11:10 AM
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Is the pump mounted directly to the pto or does it have a drive shaft connecting them?
Not knowing the brand and model of your pto it hard to say if it's clutch operated or direct direct gear engagement.
There's a gear in the trans that drives a gear in the pto, if you where having issues with these you would have heard a bunch of grinding and gear noise, you would also have metal in the trans fluid.
Any issue your having will most likely be in the pto or pump, not from the transmission.
You probably have ether bad clutches in the pto if it has them, stripped splines where the pump mates to the pto, or a sheared key in the pto shaft.
Get under there and look to see what you have and get the numbers off the tag on the pto.
 
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Old 08-10-2018, 03:29 PM
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Originally Posted by Destroked 450 View Post
Is the pump mounted directly to the pto or does it have a drive shaft connecting them?
Not knowing the brand and model of your pto it hard to say if it's clutch operated or direct direct gear engagement.
There's a gear in the trans that drives a gear in the pto, if you where having issues with these you would have heard a bunch of grinding and gear noise, you would also have metal in the trans fluid.
Any issue your having will most likely be in the pto or pump, not from the transmission.
You probably have ether bad clutches in the pto if it has them, stripped splines where the pump mates to the pto, or a sheared key in the pto shaft.
Get under there and look to see what you have and get the numbers off the tag on the pto.
Destroked, the pump is mounted direct to the pto which has gear drive, not clutches. Still trying to find where we hid the pto in the shop to check numbers. Right now pump and pto are off the truck so it's driveable not taking up space in the shop. I'm still trying to figure out why it would dump part way in the mornings and once I got it going all the way up it was fine for the rest of the day which would be multiple loads. Bought this truck to haul stone to a site for new barn and winter feed yard. Used it to haul 110 loads from a gravel pit about 8 miles one way to the farm. Most days I was able to make 4-6 round trips.
 
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