Help With Sudden Onset Of Roaring Noise W/vibration In Body

PinkRacer · December 3, 2008

Hello. Hopefully somebody can help out, as I'm currently stumped.

Truck is a 1999 GMC Yukon 4x4 with aprox 215,000km on it.

Over the last week the truck has developed what I can only describe as a "roaring" noise while in motion. It sounds like really intense/loud tire noise. Also, you can feel a vibration in the floorpan though your feet, but nothing in the steering.

Noise and vibration seem to only appear while truck is in motion, but appear to be RPM/throttle dependent, and roadspeed makes no difference. (You can hear it at 15km/h). If I'm coasting at low RPM, no noise, but get on the throttle, stay on a constant throttle or coast at higher RPM (i.e. on the highway) and it's there. The noise is always present, but the vibration seems to come and go.

Noise and vibration get worse when truck is put into 4WD.

Noise appeared on the Thursday just past.

I had put new tires on the truck (Dunlop Radial Rover RVXT, stock size, LT, not P) last Monday, so at first thought it was tire noise, but I had the same tires on a previous truck with no issues, and the noise was not there until a couple of days after the tires went on. Fact I feel the vibration through the body and not the wheel leads me to believe the tires are not at fault.

I put new hubs/bearings in the front on both sides this past Saturday (had the parts for a while and needed to be done) and the problem seems to have gotten more noticeable since. Not sure if it's as a result, or is coincidence.

Put new U joints in the driveshaft about 9 or 10 months ago.

In summary the noise seemed to just appear while driving last Thursday, and then got much more intense Saturday/Sunday after replacing the hubs.

I'm thinking maybe something in the front differential, but honestly have no idea where to begin or what to check.

Any ideas? Thanks in advance

markw8 · December 3, 2008

I'm not a tech, but it sounds like the clutch on the cooling fan has locked up. Raise the hood with the engine off and see If you can turn the fan. If it won't turn, this is most likely your noise.

Mark.

txab · December 4, 2008

Already answered in your other post.

PinkRacer · December 4, 2008

Mark: Thanks for the idea. I just checked and the fan seemed to move by hand. A little bit of resistance, but I've never tried to move it by hand before, so can't say if it's abnormal or not.

txab: Which other post?