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

    Feb 14, 2018
    China Spring, TX
    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

    Dec 18, 2011
  3. Chubby Fly

    Chubby Fly Medium Load Member

    Nov 25, 2019
    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

    Jul 25, 2013
    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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