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cfd511

Pto for mack 688

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I have a 2001 Mack 688 with the 400 and 18 speed mack tranny. The truck was an old county plow but still in great shape . i painted the frame ect. My issue is I'm trying to make the truck nice but these trucks had the hydraulic pump running off the front of the truck which makes the number stick out. This pump is a two stage which i don't need anymore because it only is needed for the dump bed and once and awhile a plow. so my question is how do i get the pump running on a pro system which is connected to the tranny. anyone know part numbers and what i would exactly need. Any help would be greatly appreciated. 

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Do you need a pto and a pump? Or just the pump?  I would check out the chelsea/parker website, give them the numbers and tooth count of the tranny and they can get what you need.

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If you are still going to plow with it.  I would not want to engage a trans mounted pto every-time i wanted to raise the plow.

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You are wanting to change the dynamics of the truck's setup. The existing pump is designed to be run with a 100% duty cycle and transmission driven PTO's are not unless designed that way and they are expensive. There is also flow division as the dump body requires much more fluid flow than the plow. You would probably be best to replace the existing pump with a "dump pump" that is transmission driven conventionally to power the dump bed, and a clutch pump on the engine to power the plow. Clutch pumps can be run 100% and be shut off when not needed.

You are going to incur some cost with the solenoid valves, or spool valves needed to make this work unless you go with an electrical driven pump but they are usually very low flow rating. Low flow would make the cyclical rate of the plow very slow to operate given the size of the cylinders used. 

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I don't mind leaving a pump connected to the front but i just need it to be smaller . the pump thats one there nows is 12 inches or more long . its two pumps in one. the front pump runs the plow and dump bed. The back of the pump (closer to motor) use to run all the components in the dump body Ie the conveyer chain and spinner for salting. If i can find a pump half the size would be much nicer so i can get rid of a lot of the unused hydraulic lines. right now i have it connnected to keep the pump from burning up. Any ideas

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I knew you were working with a multi function setup from your original description. I didn't know about the apparatus at the rear. Sounds like you have two pumps driven by a common shaft directly powered by the engine crankshaft. These are designed to move fluid constantly as you have covered by interconnecting the hoses together. That is called a "tandem" style pump if gear, or vane type. A piston type pump is much different but you've not said the pump is round so assuming it is a gear type pump.

I would like you to get a measurement of time it takes to dump your bed at the engine rpm you like. You can adjust this at leisure. Then post a few photos of the bed, the hoist cylinder(s), diameter of the hoist cylinders, and stroke length of the bed lifting cylinders. We can move along to sizing a pump/pto after the hardware in place is evaluated to work with. Don't worry about the plow functions at this time but post up some photos so I can see what you are working with.

There should be a tag affixed to that pump and relay any numbers you find.

What functions are you wanting this truck to perform? Dump, plow, and that is it, or are there other options like a bed vibrator, conveyor, spinner, wings, etc?

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I don’t use conveyor or any of that stuff anymore. Will get pictures in am

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