2001 Z71 Vibration

centurion350 · July 8, 2011

I have had this Silverado since it had 27000 miles. It now has 141000.

Very good truck except for a vibration that has recently gotten worse. It has always had some of this vibration. The truck is a 2001 Chev Silverado Z71 short wheel base with the composite bed. Automatic with all options and all still work.

I have replaced the wheel bearings, balanced the rear driveshaft, replaced u-joints, replaced tires, replaced wheels, changed fluids to all synthetic, new rotors and new pads. I have had the tires balanced several times and have had the road force balance also. I have had the dealer install the "ears" to see if they could hear a vibration. When on 4 wheel jack stands tied to the floor at the axels, no vibration. At 57 mph on the road the vibration starts and gets worse to about 63 mph and then reduces to about 70 but does not go away.

This truck has been in several local shops and the dealers and at this time I am waiting on time to load the truck to a dynomometer for a running check.

It seems that one more thing is true with the truck.....when i corner, at road speed, the vibration seem to lessen some but not a great deal. Almost all of the vibration is felt in the seat and very little in the steering wheel.

appreciate any help.

Mckenzie · July 8, 2011

Bad shocks maybe? How bad of a vibration is it?

ChevyTech77 · July 8, 2011

Going to need more information than that.

How EXACTLY do you duplicate the concern? Is the vibration vehicle or engine speed related?

Short wheelbase? Composite bed? I can only assume that it is a standard, or extended cab, with a short box/stepside bed on it??

Is the vibration present with the transmission in neutral, coasting down from speed? Same with the engine off?

What engine size? 4.3's were especially known for vibrations especially in std cab short box trucks.

Really, really difficult to diagnose a vibration via the internet, imo but, some more information about it might lead to a half way educated guess, at the very least.

centurion350 · July 9, 2011

Bad shocks maybe? How bad of a vibration is it?

thanks but i have put two sets of shocks on the truck, most recently about 15000 ago and they were Bilsteins

centurion350 · July 9, 2011

Going to need more information than that.

How EXACTLY do you duplicate the concern? Is the vibration vehicle or engine speed related?

Short wheelbase? Composite bed? I can only assume that it is a standard, or extended cab, with a short box/stepside bed on it??

Is the vibration present with the transmission in neutral, coasting down from speed? Same with the engine off?

What engine size? 4.3's were especially known for vibrations especially in std cab short box trucks.

Really, really difficult to diagnose a vibration via the internet, imo but, some more information about it might lead to a half way educated guess, at the very least.

centurion350 · July 9, 2011

Going to need more information than that.

How EXACTLY do you duplicate the concern? Is the vibration vehicle or engine speed related?

Short wheelbase? Composite bed? I can only assume that it is a standard, or extended cab, with a short box/stepside bed on it??

Is the vibration present with the transmission in neutral, coasting down from speed? Same with the engine off?

What engine size? 4.3's were especially known for vibrations especially in std cab short box trucks.

Really, really difficult to diagnose a vibration via the internet, imo but, some more information about it might lead to a half way educated guess, at the very least.

Guys

thanks for the responses.

The truck is a standard cab, short wheel with a 5.3 liter.

The vibration is speed related.

Shifting to neutral does not change it at the speed it is vibrating, i retried this today.

The truck has 265x16 Michelin tires on it but the vibration was there before the tires were installed.

The dealer has said that the next step is to replace the limited slip clutches, but this does not make too much sense to me.

I keep this truck up very well and anything that breaks is fixed quickly and with GM parts.

One thing i checked today also was the tire pressure and balance again. $45 dollars later i know the tires were only out of balance very little less that a 1/4 ounce (but i think this could be because i did not go to the same shop as 3 weeks ago) and if i raise the pressure to 38 psi in the rear tires the vibration gets worse at a lower speed.

Again thanks for the help.

robert

centurion350 · July 9, 2011

Bad shocks maybe? How bad of a vibration is it?

thanks but i have put two sets of shocks on the truck, most recently about 15000 ago and they were Bilsteins

sorry, you asked how bad the vibration is. At about 64 mph if you lay your cell phone on the center console it will move from side to side of the tray on top. I have a good luck charm hanging from the mirror and that charm does not move only in the seat.

blacksierra01 · July 9, 2011

Have you checked the rims for bends? and have you checked the axels to see if they are bent? I ran across this problem on a friends truck and turns out he had a bent axelshaft in the back.

centurion350 · July 9, 2011

Have you checked the rims for bends? and have you checked the axels to see if they are bent? I ran across this problem on a friends truck and turns out he had a bent axelshaft in the back.

have rotated the tires and rims on machine to check for true......almost perfect and this is the second set of rims on the truck.....both times it vibrated.

checked the rear axels at the time i replaced the bearings ...... good to go on a lathe.

changed bearings in the front and checked the shafts in front for true but hard to do as an assembly.

another technician said to take the drive shaft off the front drive and see if it still vibrates. the dealer said this is a no-no for an automatic truck.

this same technician said to take the rear drive shaft out and drive the truck with just the front. the dealer said this is a no-no also.

thanks

Mckenzie · July 10, 2011

Are your torsion bars cranked all the way?

centurion350 · July 14, 2011

Are your torsion bars cranked all the way?

pretty close, not quite

wavery · July 14, 2011

I am thinking driveshaft also. They should be able to diagnose anything drive-train related on a hoist.

Mckenzie · July 14, 2011

Maybe try putting your t bars back to stock settings

ChevyTech77 · July 14, 2011

Lift the rear of the vehicle and rest the rear axle on jack stands, on a solid surface of course, so that the tires are off the ground. Run the vehicle up through the gears to the speed in which the vibration is normally present. Is the vibration still there?

centurion350 · July 16, 2011

Lift the rear of the vehicle and rest the rear axle on jack stands, on a solid surface of course, so that the tires are off the ground. Run the vehicle up through the gears to the speed in which the vibration is normally present. Is the vibration still there?

earlier in the discussion i metioned that i have already did this twice. it is as smooth as a quiet lake on Jack stands. have did it on all four.