rack & pinion seems loose when engine is off??

Discussion in 'Trucks [ Eighteen Wheelers ]' started by pbrstreetgang, Aug 2, 2020.

  1. pbrstreetgang

    pbrstreetgang Light Load Member

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    Sep 7, 2007
    California
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    (yes i actually do have rack & pinion steering. i understand this is very rare.)

    even when the truck was brand new, there was a decent amount of play when you twist the drive shaft (engine off). with the engine on, however, there is very little play...twist the drive shaft just a tiny tiny bit and the wheels move. the problem is, whenever i get an inspection, they do it with the engine off and i always get the weird dirty looks and i have to explain that it will help to turn on the engine.

    can someone please explain why there is such a difference? is it supposed to be this way? with gearbox steering (which i do not have) is there any difference between engine on and off?
     
    Last edited: Aug 2, 2020
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  3. Inderjit

    Inderjit Medium Load Member

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    I would guess that the slack in the steering is the hydraulic valve for the power assist opening to allow flow to either end of the rack.
    Could you post a picture of the steering gear and what make of truck?
    I have been a truck mechanic for over 40 years and I have never seen a rack and pinion gear in a truck.
     
    pbrstreetgang Thanks this.
  4. pbrstreetgang

    pbrstreetgang Light Load Member

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    California
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    thanks very much. it's a 2009 cascadia. they only did the rack & pinion for one year i think. i am home and not with the truck right now but i can try to post a pic later. what part of the steering do you want me to get a picture of specifically? there really is no steering gear per se...it's just the basic rack and pinion setup with the rack, tie rods, steering shaft etc.

    btw what happens in a normal gearbox-steering truck when you twist the steering shaft (and does it make a difference with engine on, and with engine off?)?
     
  5. pbrstreetgang

    pbrstreetgang Light Load Member

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    Sep 7, 2007
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  6. Inderjit

    Inderjit Medium Load Member

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    The steering input shaft in a normal steering gear is made in three pieces an upper and lower shaft that has an internal torsion bar that allows the top shaft to turn separate of the lower shaft allowing the top shaft to operate a hydraulic valve controlling the flow to either end of the rack piston. There will always be some free movement with the engine stopped.
     
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  7. pbrstreetgang

    pbrstreetgang Light Load Member

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    Sep 7, 2007
    California
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    that's good to know. thanks for all the info. i wonder if less-experienced mechanics are aware of these things, and i wonder why no one ever wants to test things when the engine is running and the steering is tight! maybe people are just too lazy to wait for the driver to turn the engine back on. anyway thanks again for the info
     
  8. magoo68

    magoo68 Road Train Member

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    st malo mb canada
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    I had a 2009 cascadia after 3 racks they put a upgraded one in it on warranty .. many trucks were converted to normal steering due to the high rack failure. Btw the mechanic told me not to turn as sharp because the rack has higher side pressure on it the sharper you turn .
     
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  9. pbrstreetgang

    pbrstreetgang Light Load Member

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    California
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    wow that's interesting, thanks. what would happen to the steering when yours kept going out? did it completely fail or just get really hard to steer? i guess i should be very thankful mine has lasted this long and still seems to be ok
     
  10. magoo68

    magoo68 Road Train Member

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    2 blew out the end seal one got very loose.. the upgraded one was more beefy and seemed fine after 3 years .
     
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  11. pbrstreetgang

    pbrstreetgang Light Load Member

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    good to know it didnt send you into oncoming traffic. thanks for the info!
     
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