1998 4WD Blazer.

Soon after starting the truck you will hear a grinding noise like gears are working at getting into their correct locations, right below the center console.

No matter the speed of the truck the speed of these gears getting the correct position will stay the same, not speed up or slow down. I have even put the car into neutral, rolled along and revved the motor, same noise.

I think the 2WD & 4WD are vacuum actuated? Do not know if this noise is related to that. Truck needs to sit a few hours or more before it will do it again.

If I let it idle for a bit it does not do it.

Any ideas???

Brian 267-516-0305

 

Have a look under hood at the throttle and cruise control cables. Make sure that they are not resting against anything on the driver side of the engine. Specifically the PCV valve tube that runs up to the lower intake manifold from the driver side valve cover.

 

Dealer said it was the vacuum actuator, used to lock front axel hubs in and out of 4 wheel drive.