humming in front end

[bluedemon]

Hi everyone I'm new to this site and to chevys. I just recently bought a 2004 Tahoe which is all wheel drive and has about 75000 miles on it. Ever since I bought it I've been hearing/feeling a humming/slight vibration from the front end. I know a little about cars but I would like to get more experienced help from this forum if possible. I'm thinking it could be either the fluid in the transfer case is low or the front axle is low on fluid or needs to be changed. I'm taking a long trip on Monday and if I could get any ideas from you guys on what I could look at I'd appreciate it very much! One more thing, I only hear /feel the vibration when I give the tahoe gas and when I let off you can hear it for another couple seconds then it goes away. This is what leads me to beleive that its something to do with the drivetrain. Again thankyou for any help you can provide me

 

[sasquatch]

it`s tough to pinpoint what you`re describing without seeing the truck but i`d start with the basics. check all the u-joints and the front wheel bearings, if they all check out ok then i would look into bigger potential problems in the transfer case or the differential.

 

[bluedemon]

How do I go about checking the U-joints? Wheel Bearings? Thanxs for the advise so far!

 

[boostaholic]

Easy to check the u-joints:
Chock the wheels
Set the truck in neutral
Grab the yoke and try to twist the driveshaft
Play should be easy to see, usually the needle bearings will develop play upon lack of grease
To check the wheel bearings or unit bearing assemblies:
Jack up the front end about 4-6"
Get a big ass pry bar or something similar to place directly under the wheel
Lift up vertically and look closely at the balljoints or the wheel bearing assembly (easier to do with another person looking for play)
Any movement is not good, inspect where the play is coming from and replace parts as necessary