Transmission grinding / chattering when going downhill

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by casemill, Feb 27, 2020.

  1. casemill

    casemill Bobtail Member

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    Feb 14, 2018
    China Spring, TX
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    I drive a 2011 peterbilt 384. When going from 40 mph to 50 mph it shakes, A LOT. After 50, it smooths out. Today is 2/27. I got new drive tires on 2/25 on the front drive axle. The back drive axle tires were put on in august 2019, six months ago. My boss replaced 3 of them, the other one has decent tread but is a little more worn than the other three. My steers are less than 9 months old as well and still have good tread. What ideas do you have that could cause this shake at 40-50 mph? Anyone got any ideas?

    Second issue: After I got the new 4 tires on my front drive axle, the transmission makes the grinding noise every time I let off the pedal or coast down a hill. New tires shouldn't change the ride height, but I'm starting to think my ride height is messed up. Any thoughts?
     
  2. Ridgeline

    Ridgeline Road Train Member

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    Dec 18, 2011
    Michigan
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  3. Chubby Fly

    Chubby Fly Medium Load Member

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    Nov 25, 2019
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    Yes if you just changed the tires on front axle and there is a big tread difference, your pinion angles are out of wack
     
    Snow Hater Thanks this.
  4. baha

    baha Road Train Member

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    Jul 25, 2013
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    Your air ride hight arm is warn out and is not letting air back out to level it out when you let off fuel petal , ck every thing u/joints and replace all warn out parts?
     
    Lab work Thanks this.
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