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Vibration in 3/4 ton 87.. what do you think?

Discussion in 'Chevy Trucks' started by mindtream, Jun 10, 2002.

  1. mindtream

    mindtream Junior Member
    Messages: 1

    Hello,

    I have a 1987 3/4 ton 2wd Chevy Suburban with a 2 piece driveshaft and a 454 engine. I have been getting a pretty severe vibration that starts as a continuos noise between 48-63 mph or so and then turns into a pulsating vibration above 63 that is sort of a waa-waa-waa sort of thing. It seems to increase in oscillation frequency immediately when I hit the gas.. the speed of the vibration is increased instantly. It is loud under load, but decreases by about 80% when coasting. There is no vibration evident when running through various engine speeds in park, or when running through various wheel speeds on a lift, but on the lift there is no load on the wheels so that would seem to be relevant. The following has been replaced or checked/repaired with no effect:

    replaced rear end
    new tires and wheels balanced and aligned
    new brakes all the way around
    harmonic balancer checked
    new torque converter and flex plate
    new trans mount
    new u-joints and center support bearing
    checked engine mounts

    I also noticed that if I put trans in neutral, I can hold the front half of the driveshaft solid before the center support bearing and rotate the back half after the support bearing about 1/8-1/4 inch or so. Is this excessive and if so, might the splines be shot?

    Would an out of balance driveshaft seem to fit these symptoms? Any other ideas / thoughts?

    Thanks,

    Darren
     
  2. Larry J

    Larry J Junior Member
    Messages: 3

    Have you had the drive shafts balanced? Sometimes they get get reversed and 180" out, when they are reinstalled.
     
  3. 455sd

    455sd Junior Member
    Messages: 3

    vibration

    i would be very suprised if it is not the tail shaft centre bearing but if it has been replaced correctly and the shaft has been balanced after bearing installation i would be looking at the diff centre pinion bolt to see if it is not loose or in a extreme case the whole ring+pinion