Help me find humming sound?

[JUNIOR-K5]

I have a 89 burban 4x4 and runs fine but when im driving and step on gas there is a humming sound. I thought it was the muffler so I replaced it and no still there when its coasting no sound but as soon as I hit the gas it humms. By the way the tires are stock.

 

[Big Blzn]

Sounds to me just like the noise I had that turned out to be the last few hour of life on one of my ujoints. Made more of a low pitched squeeling noise but i'm sure the noises can vary. Even if i got under the blazer and tugged in all directions it seemed fine and less than a day later, BOOM! Blew the ujoint and the slip yolk. Same thing with noise under the pedal and nothing while coasting.

 

[b454rat]

Pinion bearing. Known to make that sound, old truck had 235k on it and was still going strong....

 

[JUNIOR-K5]

Thanks guys ill change u-joints tomorrow and if that dosent work I guess pinion bearing kinda figured it was bearing but hoping u-joints will fix it.

 

[Big Blzn]

Let us know what you find.

 

[Hogback Fabrication]

To check the pinion bearings, see if there is any in/out or side to side play in the pinion yoke; there should be none. There will be a little rotational play, that's normal.

 

[GNERGY]

Do you have a worn out motor mount and when you give it gas it is touching metal to metal and you are hearing engine noise ( vibration )
Tarey

 

[JUNIOR-K5]

Thanks guys for the replys I have a set of new ujoints and motor mounts which I will install. But on the pinion bearing if it has no side to side movement or in/out the bearing should be good right.

 

[Drey]

My K5 does that too...when the pinion bearing pukes itll get a 14FF to replace it.