Drivetrain noise on deceleration.

[Lapper]

Hi folks,

I just purchased a 1972 K20 4x4 4 speed fleetside longbox the other day, and am "enjoying" the process of importing it into Canada. I'll post my import experience once it is complete in another thread.

The vehicle made the cross-state trip across Washington, but makes a kind of howling sound when decelerating. Imagine someone saying "WHOOOoooo" and you have the idea. Now I am left with the task of diagnosing said sound. When I push in the clutch, the noise goes away, so I guess that rules out the engine and front axle. That leaves the transmission, transfer case and rear axle as possible suspects. It is louder at higher speeds.

Any troubleshooting tips would be greatly appreciated.

Thanks.