Vibration when doing closed curves

[machadosl]

Hi guys,
I have acquired on march of this year a 2004 Z71 Suburban, it is a nice car but it has the inconvenience that is a very rare car here in Brazil.
Well, I have a problem, that I don't know if it is mine or of the car, but every time I make a closed curve, as parking on small places, the car starts vibrating, it seems it comes from the axles, and the car turn on the 4WD if it is on the auto mode. If I press the 2WD this vibration stops.
I have already changed the oil of the front axle but not from the rear axle as I am waiting the gasket for it to arrive from the US.
Can any one here give me a help?
Thank you,
Sergio

 

[Vette66]

This is Normal. When in 4WD it locks the front end. By locking I mean it does not allow the front wheels to turn independent of each other. So they both turn and the same speed causing one to drag, you then feel the vibration. It is not really good to have the truck in Auto or 4WD when not needed.

 

[machadosl]

Thank you very much Vette66, I was supposing it was a problem of the driver here (Me!), but I wasn't sure as this is the first car that I have with automatic 4x4 and the manual does not have anything about.
Once again thanks,
Sergio