2500 HD 4X4 Vibration - Rant

[Zrxpilot]

Ive had this annoying vibration since I bought the truck a few months ago. 80,000 miles, 8.1 and pampered. Assumed a tire balance would fix it to give you an idea how bad it is. Can live with it.

 

Anyways, the wife brought it in to a local tech for diagnosis when I was out on a buisiness trip. Was told it was the rear hub. Apparently the had the back on jackstands and ran it, noticed some wheel hop and assumed a bad hub.

 

Did some checking on the net and read the numerous reports of others having issues with the front (front hub issue, im well versed). Checked it out and found nothing wrong. Both fronts spin freely with no significant lateral movement when yanking on the wheel in any direction

 

Went to the rear hub. Took it apart clear to the hub. Caliper, rotor and axle out. Bearing spins like it should with no visible damage anywhere. Thus hub is a tough unit. Relatively small diameter. Cant see that thing getting bent no matter what you do.

 

Made a makeshift micrometer and inspected the rotating assembly on at least 3 axis. Found nothing more than maybe a .020" inch peak to valley out of roundness/ out of flatness. .020" doesnt seem like much to me. Its quite a bit less than a 1/32". Concluded tech missdiagnosed the issue and probably am not very welcome at his shop anymore.

 

Reinstalled everything and replicated tech's procedure. Rear of the truck raised up and on jackstands. Wheels on and ran it. Max tire rpm is idle in gear whatever that is. Pretty fast.

 

Put my makeshift micrometer and the only significant deviation I found anywhere was on the outside diamter of the tire (wheel checked out fine) and along the sidewall surface. Both back wheels producing nearly identical results. Max peak to valley of tire out-0f-roundness about an 1/8.

 

1/8" doesnt seem like much. Or is it? Tires have less than 5000 miles on them. Installed by dealer after a trade in. Long box standard cab that sat on the lot for awhile with a ton of armor all on the tires.

 

Taking it in today to have the rears balanced like I would have thought the tech would have done right from the get go. Been reading some about dynamic balancing. Going to try that. If that dont work I am just going to asssume the tires are out of round and try do a few nasty burnouts to balance the tread.

 

Any thoughts?

[seasled]

driveshaft threw a weight?

~sea

[markw8]

Your methods don't seem reliable to me. That said, .020 runout on the axle flange COULD/WOULD be a lot more at the tire tread. Variance in the side wall of 1/8" means nothing. Exactly how accurate is your makeshift micrometer?

 

Mark

[Zrxpilot]

^ Its pretty accurate. My guess +0 and -10. Placing a fixed object next to something rotating and looking at the variance of the gap as the assembly rotates seems like a reasonable approach. Its the same method that turbine manufactures use when they inspect turbine blades. By no means an expert. I just dont expect a new hub to be any less than this. Max peak to valley at the wheel outer rim was near identical to the max peak to valley distance found at the hub. This was not the case at the tire outside diameter or at the sidewall of the tire.

 

Called a chevy dealer and they also advised that a new one probably wouldnt be that much better.

 

Called around and found a shop that does dynamic balancing (whatever that is...apparently something new). Explained to the tech what was up and asked that he put his best foot foward. End result, the back tires were off by 1.75 oz.. Fronts were off 3.5 oz and 2.75. The balancing took out 75% of the vibration.

 

I believe the remainder to be vibration to be caused by the out-of-round of the tires.