Noise Diagnosis Assistance

[TheMythofUtica]

Hey folks, I have a noise coming out from under my truck that I'd like to pinpoint. First, it's a 1999 Yukon (OBS) 4wd with 3.73's and a factory limited slip. The noise goes like this:

 

At speed around 25-55 when crusing normally I get a "whirring", maybe you could call it a light "grinding". Now lets say there is a dip in the road, maybe a series of dips. As I go over the dips, the noise appears as the load comes off the suspension then back down. Know what I mean? So as I sail over the dips I get - "Whirrr....nothing....whirrr....nothing...whirrr....nothing". I had a 1989 K5 Blazer that blew a 10-bolt, so I know what that sounds like, and I dont think that this is the same. My early estimations include wheel bearings, the rear u-joint or maybe a rear brake problem.

 

Any help or ideas from anyone would be great. Thank you!

[ManyCamaroz]

A whirrr or a grind is described differenty by many people. Could be a prop joint going south. or maybe something rubbing on your driveline.

[asilverblazer]

Just another idea but my truck makes a strange noise on one road I drive down and when going into the valley of the hills on this road the down ward inertia of the truck puts more force on the tires, same as your "whirr-nothing-whirrr..." I have decide it is tire noise because it is only on this single road that I notice it. Point being maybe as the tire load increases by additional g-forces it transmits a different road noise.. maybe? I don't know...

[Shaners]

Depending on the milage on your truck, it wouldn't surprise me if a wheel bearing isn't going bad.

[Tucson_02Silverado]

Does the noise come from a specific "corner" or is it all around?

 

Is it road noise from the tires? Does the noise exist on dirt roads?

[budhayes3]

And does the noise change pitch when turning right and left? If so, which way (right or left) affects it more?

[TheMythofUtica]

No, the noise does not change when turning and I also don't beleive it to be the tires as I just got new ones and the noise stayed the same. It also doesnt seem to come from any particular corner of the truck. I'm leaning toward a bad rear wheel bearing or u-joint. The truck has 71,000 miles and the noise has gotten a little worse in the last two months. Throttle input change (power to driveline) does not affect the noise either, and it seems to be worse around 45 mph. Thanks for the input so far guys!

[ManyCamaroz]

Let me tell you what my problem was now that I've read your post again and got to thinking about it. I had this rumble/vibration that appeared to be coming from the rear of my '99 OBS Yukon. At first I thought it was the u-joints so I changed them. There was some slight wear but not to bad and the sockets still had grease. Problem still existed. So I was thinking a wheel, axle, carrier or pinion bearing was failing. I took it to a local Chevrolet dealer (under warranty or so I thought, the warranty company had gone bankrupt). The dealer said it was bad tires. I had Michelin LTX/MS tires with still about 20k miles left on them, alway's balanced and rotated at 5k miles and always balanced out easy. The tire wear was flat and even. So, I went ahead and replaced the tires. Problem still existed. I called the dealer that I bought the now non-existant extended warranty from (Arnold Palmer Cadillac) and lucky me, due to APC's fine reputation they would make any warranty repairs out of their pocket. I took the truck over for them to inspect as I had several warranty covered problems to repair. He said it might take a week to get them all corrected. They sent me home in a '05 Cadillac SRX loaner . The next day they called and said it was the tires, they could not find a problem with the rearend. I explained that the tires were less than 500 miles old. He said they would look into it further and get back with me. Several day's later he called and said:

 

 

You are not going to believe me but we found your problem. One of our techs. came from a GMC dealership and remembered a TSB concerning the same symptoms. Now get this! The foward roof rack bow was too far back and was causing wind turbulence between the foward and aft bows, and that is what was creating the rumble. We moved the foward bow to the front of the rack and the aft bow to the rear, and the problem is solved.

 

I'm thinking but agreed to at least give him the benefit of the doubt.

Problem no longer exist. .

 

You might want to check your bows. I cannot ever remember moving mine and can see by UV fading where they were prior to their adjustment. Maybe the vehicle is settling some due to wear and tear.

 

Kept the Caddy for one week but yearned to have my Yukon back. If I had a choice between my obs or the new Caddy and had to keep it. I would take the Yukon. I love a nice Caddy as my wife has a '97 eldorado ETC but it ain't no Yukon.

 

Sorry so long but I'm out of town working and have nothing to do.....

 

GOOD LUCK!

[TheMythofUtica]

Excellent reply man. I will check the roof rack and do some screwing around with it. Seems too good to be true, but hey, it's worth a shot. I'm still skeptical because it seems like I can almost feel it (my noise) in the floorboards...but anything is worth a shot. I'll let you know if this helps. Thanks again!

[Wingnut]

That has got to be one of the strangest causes for noises/vibration I've heard in quite a while.

 

Bravo to the tech that figured that one out.

[ManyCamaroz]

Excellent reply man. I will check the roof rack and do some screwing around with it. Seems too good to be true, but hey, it's worth a shot. I'm still skeptical because it seems like I can almost feel it (my noise) in the floorboards...but anything is worth a shot. I'll let you know if this helps. Thanks again!

 

<{POST_SNAPBACK}>

 

 

 

Vibration was one of my symptoms, I could feel it in the pedals/floorboard. That is why I was leaning towards a bearing failure. Move your front bow all the way foward and the rear all the way to the rear and test it out. Let us know what you find.

[sonjaab]

JD..........I remember that roof rack vibrationissue posted elsewhere on

these forums ! There was a TSB also !

You have a great memory !.................geo

[ManyCamaroz]

JD..........I remember that roof rack vibrationissue posted elsewhere on

these forums !  There was a TSB also !

You have a great memory !.................geo

 

<{POST_SNAPBACK}>

 

 

 

It just happened to me last month. The tech has a good memory. Back in my earlier days when I worked at a dealership the old timers would have let a green horn scratch his head over it a couple of day's and have big laugh while he pulled his hair out troubleshooting it.

 

I have a good memory, it's just short as heck.

My reason.... I was a teenager in the '70's .

 

Dennis

[TheMythofUtica]

Well, I haven't messed with the roof rack bows yet, but I did load a Christmas tree up there today and noticed no difference, the noise was still there. The tree covered the whole roof so that wind couldn't have gotten underneath it to cause any havoc with the roof bows. But we'll wait and see what happens when I actually move those around. I'll keep ya'll posted.

[TheMythofUtica]

OK, had to use 4wd the other day and when I did the noise got wicked bad. It might not even be the same noise, but I think it is. Like a really bad griding/humming noise when in 4wd. Not Auto 4wd, but regular old 4wd. What do you think?