4WD Frontend Noise

[jeepstud]

Hello Guys-

 

2002 GMC Sierra SLE with Autotrac, 5.3L. Recently I have been having some new noises that sound to me like expensive noises. To aid troubleshooting I will try to provide as many details as possible.

 

The noise itself is somewhat of a rattling/ratcheting/tingy kinda noise. It does not sound or feel like something is binding then releasing (pop). It is not a growl (although mine does growl as well) Instead I guess it sound more like a baseball card in bicycle spokes, it is rythmic and seems to change frequency with speed. It is fairly loud, loud enough so that you could hear it if i rolled up next to you.

 

The noise does not occur in 2wd at all. The noise will occur in either Auto or in 4HI. I have not tried 4LO. As near as I can tell the 4WD appears to be working correctly. The auto kicks in smoothly and bites hard, as does the the 4HI. The noise only seems to occur as I coast down or maybe coast around a corner. As speed slows down it starting making that tinking noise. To me it sounds like it is coming from the drivers side (although that is where I am sitting).

 

I changed the front end oil and didnt see any chunks of metal and no change with the noise. I checked the 4WD actuator and moved in and out. I pushed on the fork the actuator moves and it felt free. I am not sure that I have ever heard CV joint noise although since the CV's spin all the time I would have expected to here the noise all the time (correct me if I am wrong). I did not see any burned out u joints on the front drive shaft and I could not get the CV's to make the noise on their own.

 

Is it possibly that some small binding when the truck is in 4WD versus 2WD is causing the CV to click? How can I check this (remove the CV and try and drive the truck?

 

 

Any help or suggestions of things to check would be appreciated.

Thanks

Trent