Loud humming sound

SUSIE SHAW

MEMBER
2004 PONTIAC AZTEK
3.5L
6 CYL
AUTOMATIC
180,000 MILES

When driving at speeds past 40/45 MPH it starts to make this loud humming noise. We replaced all the wheel bearings and brakes. It sounds like it's coming from directly under car in the middle. We took it to a shop and he said we needed a new transfer case. But we have no slipping or leaking at all. Please help.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

Is this an AWD model? If it has a transfer case, it must be. As far as the noise, approximately the center under the vehicle is where it would be located. Have you checked the fluid condition and level or tried to service the unit first?

If you look at the attachments below, they include the directions and pics specific to this vehicle for servicing the transfer case. If you simply want to check the fluid, only remove the fill plug (top one/see pic below). Fluid should be at the bottom of the threaded portion where the fill plug goes.

Also, if you add fluid, you have to use the correct fluid type for this vehicle. Here are the manufacturer's specifications for the fluid:

2004 Pontiac Truck Aztek AWD V6-3.4L VIN E
Fluid Types
Vehicle Maintenance Fluids Fluid - Transfer Case Specifications Fluid Types
FLUID TYPES
Transfer Case. Synthetic VersaTrak Fluid GM P/N 12378514

Start by making sure it is full and the fluid is clean. If it has never been serviced, try that first. Also, if it is loud enough for you to record, do that and upload it for me to hear.

Let me know if this helps or if you have other questions.

Take care,

Joe

See pics below.

Images (Click to make bigger)