Low pitch humming noise when in Strait 4wd

[06Radoz71]

I’ve had my 06 Silverado 1500z71 for about 6 or 7 months now and have never noticed this problem until about one month ago. In regular old 2wd the truck rides and sounds like a dream. When I engage strait 4wd there is a loud low pitched hum. It started out to be just a small noise and has now become louder. The noise is also not much different in Auto 4wd. I am almost 100% sure it’s coming from the front drive shaft or diff somewhere because the transfer case as we all know is not engaged in auto 4wd, but the diff is. As I drive up around 30mph the noise is not really noticeable but when I slow down it gets much louder. There is also a big drag when I’m in 4wd and Auto too, (truck slows down much quicker) I changed front diff fluid and it look ok, small amount of powdery metal dust on drain plug as most trucks have anyways. The pinion is tight and there is no play, the actuator seems to be ok because it sounds normal when engaging. U joints maybe? truck has 78k miles

[gmtech4]

where are you driving when in 4wd?

[06Radoz71]

On normal snowy roads

 

[ChevyTech77]

The front diff's that year are known for bearing issues. Pinion and side differential bearings both can make noise in them.

[00Silverado4x4]

Sounds like my truck from day one. Not to say you don't have a problem just saying sounds just like mine.

Have 91k+ miles and still trucking.

[06Radoz71]

The front diff's that year are known for bearing issues. Pinion and side differential bearings both can make noise in them.

 

 

If the bearings were bad, shouldnt there be play in the pinion? Or not always

[ChevyTech77]

Not always. Pitted races and rollers will cause noise and no excessive play. If you have the means of pulling the front diff yourself (fairly easy, actually) and getting it to a diff shop, they probably wouldn't charge you much to split it and check it out. If it's bearings it's best to do it now before it gets worse and wipes out everything in there.

 

NOTE: There will be some noise in 4WD in any vehicle but if this is something that was NEVER there until now, I'd say you have something going wrong.

[06Radoz71]

Ok ya that does make sence. Although yesterday i pulled the front drive shaft, and u joints felt smooth. But i drove it after i put the shaft back in and now it doesnt do it when in auto 4wd. It wont do any damage if i put it in 4wd and drive it without the front driveshaft will it? I want try to better locate the noise.

[ChevyTech77]

No.

[zedbear]

Ok ya that does make sence. Although yesterday i pulled the front drive shaft, and u joints felt smooth. But i drove it after i put the shaft back in and now it doesnt do it when in auto 4wd. It wont do any damage if i put it in 4wd and drive it without the front driveshaft will it? I want try to better locate the noise.

 

 

I wouldn't do it......

 

I pulled my front driveshaft when trying to isolate some noises. I took it for a ride and engaged 4wd and there was a loud grinding/gear clashing sound when I pressed the button. I quickly hit the 2wd button and it stopped.