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

mindtream

Junior Member
Location
Illinois
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
 

455sd

Junior Member
Location
australia
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
 

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