Mechanics

1/2 TON REAR END VIBRATION

1999 Chevrolet Silverado

1999 1/2 ton silverado 5.3 vortec 110,000 mi.

I was getting a vibration from the rear end at ~40 mph and ~70-75 mph. It felt like the right rear tire was out of balance. Took it in for balancing and was told the tire was separated and " checked". Needed new tires. Tires were old and down to were bars so I got some E rated Pirelli 265-75-16's on it, but the vibration didn't go away. Had the tires rotated and balanced 3 times and they even force balance them. Still had vibration from right rear. That's where I feel it's from. Vibration at 70 mph decreased but was still present.
Checked shocks against new set and compression and extension were fine. Kept old shocks on. Removed rear drive shaft and had it balanced. Was fine. Checked u-joints. Service guy said they were fine, but rear one would need replaced in a year or so. Replaced rear U-joint just to eliminate this variable since it'd need it soon anyways. Still had vibration.
Pulled rear brakes and rotors. Left rear was fine. Right rear rotor showed uneven glazing on outer pad area. Light color towards hub and dark glazing toward outer 2/3's of pad surface. Parking brake pads quite worn and shiny surfaces noticed on inside of rotor in 2 spots 180 degrees from each other. Parking brake seemed hung up. Lubed it and got it moving freely again.
Replaced rotors, pads, and parking brake pads. Actuated parking brake several times and tested with rear end in air. When reset, tires rotated freely. Took for test ride. Still vibrated.
Vibration is worst during first drive of the day when ~40 mph is achieved. After 5 miles or so, the vibration reduces but is still present when 40 mph is achieved again.

Suggestions?

thanks,

dave
Avatar
DaveL2
October 5, 2007.




After all that troubleshooting, I simply tried running more air in the tires. The service center had 40 psi in them and I pumped up the rears to 70 and the fronts to 60 and the vibration is almost totally gone. I think that with the low air pressure, I may have been getting small flat spots that would vibrate and then go away after the tire trued itself back up.

Anyways, I believe the only vibration I now feel is the road thru the E rated tires.

If I had to do it again, and I will someday, I'm going to go with a C or at most D rated tire for the smoother ride. I just couldn't pass up the deal I got on this set though.
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Tiny
DaveL2
Oct 8, 2007.
E rated tires are an overkill on a 1/2 ton truck. It will also take a minimum of 10 miles driving to allow the tires to " warm up" to reduce vibrations.

Dennyp
Oct 9, 2007.

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