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Mack GU713 Power steering


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I have a 2012 and 2013 mack granite triaxle dump truck with 385 tires on the steer axle I noticed the other day while making a u turn with a load of stone I could not turn the steering wheel unless the truck was moving it was like it had no power steering I checked the oil levels and they were fine I have older granites with same size tires and it is not an issue was wondering if anyone has any idea why

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  • 3 weeks later...
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I have a 2005 CV713 Granite tri-axle and mine started doing the same thing as yours. I have 425's on mine. A loader in our rock yard backed into my truck and damaged a lot of front end stuff including the steering pump which is bolted to the right front side of the motor.After fixing the truck (including a new steering pump) the problem completely went away. I would try changing the pump out. They are'nt real expensive.

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  • 6 years later...
18 hours ago, Mvnfast728 said:

Still at the dealer I guess? 

A little snarky for your first ever post.

Much more productive to ask if there is a follow up to the situation because you might be having a similar problem.

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Jim

It doesn't cost anything to pay attention.

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I have a 2000w kenworth t800 same issue steers fine with front end jacked up but steers real hard (not at all) unless it’s moving king pins seem good reservoir has fluid changed reservoir filter ( was nasty) still steers hard when not jacked up does this also sound like the steering pump? Reel addiction how did you make out at the dealership? 

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Could be a steering pump, or seals on the internal spool valve of the steering gear. Easy enough to plumb in a pressure gauge and relief valve setup to test the components.

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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16 minutes ago, Rob said:

Could be a steering pump, or seals on the internal spool valve of the steering gear. Easy enough to plumb in a pressure gauge and relief valve setup to test the components.

Plumb in pressure gauge on outlet hose of pump? What is normal pressure any idea? It’s just weird it will steer perfect when tires are off the ground .

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1 minute ago, Sdecker85 said:

Plumb in pressure gauge on outlet hose of pump? What is normal pressure any idea? It’s just weird it will steer perfect when tires are off the ground .

Yes on the pump for one gauge to test pump output. Usually about 1200-1500psi the system should be relieving internally. If pressure is not correct internal to the system there will not be enough hydraulic assist and greater effort from the driver will be required. No weight on the wheels should allow them to turn almost effortlessly. 

Near any service manual will have a power steering test setup included.

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Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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You need to discount the weight off wheels thoughts. If there is no resistance to the tires turning, there will be no rise in hydraulic pressure to force them to turn. Hydraulic flow determines how fast you can turn the wheels, hydraulic pressure determines how much effort the system requires from the driver meaning higher pressure equals less driver input. 

Dog.jpg.487f03da076af0150d2376dbd16843ed.jpgPlodding along with no job nor practical application for my existence, but still trying to fix what's broke.

 

 

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With the wheels off the ground my 1973 Mack will turn effortless, and it has no power steering!!! The trucks  weight on your tire contact patch is the only thing that generates resistance to turning the wheel. Unless you've broken the steering box, in which you'd likely feel a clunking when turning the wheel.

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