humming noise, U-joint?

[bhuff30]

On my 97GT, sometimes when I'm slowing down for a turn or stop, I can hear this humming sound. It sounds as if something is vibrating very quickly, but I don't feel any vibration in the car. It normally happens anywhere from 20-40mph, and only when I'm slowing down. The noise does no change if I put the clutch in. I didn't get to check to see if the noise goes away when I start accelerating, but I've never heard it durning normal acceleration.

So any guesses? My best guess so far is a U-joint that is getting sloopy.

 

[flstang65]

a drive shaft is easy enough to to drop and inspect the u joints. that's where i would start.

 

[COramprat]

The u-joint usually makes noise at the same RPM. If it is making noise on decel or accel around the same point then it is like a bad u-joint.

 

[wingless wonder]

It's humming because it doesn't know the words.

But seriously, if the noise is there when the car is in or out of gear I don't think it's a u-joint.
Wouldn't the sound be greater if it was under load? What about a wheel bearing?

 

[bhuff30]

I've heard plenty of wheel bearings, and it doesn't sound like that. Wheel bearings are higher pitched and this noise is low and deep. To me, it sounds like it is coming from the center of the car. I don't think it's the transmission because taking it out of gear makes no difference... I hope it isn't the rear end because that was rebuilt less than 20k miles ago.. so that leaves the U-joints. Guess I'll have to crawl underneath and see if I can get the driveshaft bolts loose one of these days. The previous times I had to pull the driveshaft, the driveshaft bolts were rediculously tight from the transmission shop.