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Isuzu vibrates on highway

Discussion in 'Trucks and Trailers' started by skipdow, Jul 9, 2008.

  1. skipdow

    skipdow LawnSite Member
    Messages: 4

    I have a 99 Isuzu NPR that vibrates loudly at 55 mph and above. I've checked the U-joints and drive shaft and can't figure it out...It is loudest at 60 mph and If I take my foot off the gas pedal the sound completely disappears until I touch the gas again. Any Ideas?
  2. jhcreech

    jhcreech LawnSite Member
    Messages: 8

    drain a little bit of lube out of diff and see if the lube has a silver tint if it does you have a ring and pinion problem. the noise is generated on the load side of the ring gear and normal on the coast side of the gear (no load)
  3. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Messages: 9,544

    Is this a automatic or standard ?

    I see your from Vancouver you may want to make a trip to a place like IWE rear ends have the diff checked.
  4. skipdow

    skipdow LawnSite Member
    Messages: 4

    It's an automatic. The diff oil was changed when I bought it about 6 mnths ago by my uncle who transported it from New York for me during the trip along with a lot of other fluids. My next check was going to be at a Differential shop.I'm a big fan of fixing things before they break, its usually cheaper then and I can choose my down time.
  5. TPS

    TPS LawnSite Senior Member
    from NJ
    Messages: 363

    When I used to drive a box truck had the same problem. It had a bad king pin on the passenger side. Vibrated the entire truck enough to give you a head ache when driving.
  6. J&R Landscaping

    J&R Landscaping LawnSite Fanatic
    Messages: 5,095

    Front end maybe out of allignment?? Maybe a tire kicked a wheel weight and that wheel is now un-balanced. Might also be wheel bearings..
  7. skipdow

    skipdow LawnSite Member
    Messages: 4

    the front suspension is 100% good, I haven't looked for missing wheel weights but that wouldn't go away with my foot off the gas. The most likely is sounding like the rear axle. thanks for the replies
  8. A Leaf Above

    A Leaf Above LawnSite Member
    Messages: 223

    Could be Tranny also or even something as simply as the tranny mount ..
  9. Garden Gate

    Garden Gate LawnSite Member
    from houston
    Messages: 23

    hey there i read your post. i have the same problem. i have a 2005 isuzu npr that does just that at about 60mph. it smooths out on even ground/ highway and then i hit just a small hole and it rumbles quite a bit.
    anyway i stopped at the dealership here in conroe , tx and a technician advised me to get 10 ply tires on it as opposed to the 6 ply i had. he also said that the bouncing is caused by the pattern formed from the uneven wear of my 6 ply. once the pattern forms it keeps wearing unevenly following that same pattern.
    a guy dropped by the same place and told him he had replaced anything and everything that looked wrong or worn and still had the same problem.
    all the best i hope this helps . i will be trying those tires soon .
  10. jkason

    jkason LawnSite Senior Member
    Messages: 546

    Have them check the steering damper, too.

    I had a vibration in my Jeep. I thought it was a wheel weight, also. The thing would shake like you were trying to hold onto a .50 caliber machine gun. Really rattle your fillings.

    Changed the damper, problem went away.

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