2001 Legacy after sitting in garage overnight   Put into reverse and you get a loud clunk in the rear. After driving for 1/2-1mile there is the normal sound when putting into reverse. Only clunks after sitting overnight. Rear axles are fine, drive shaft only has 3/8” rotational play. I am stumped. Fluid is fine. 

next morning, maybe a helper could 'pace' the car to determine if the noise is central (maybe diff mounts?) or on one side (brake or suspension?)

do you set the parking brake?

many parts could be suspect on a 21 year old car.

4 hours ago, 1 Lucky Texan said:

do you set the parking brake?

Good question! Could easily be that!

Does the clunking go away after the mile?

Cold high idle results in higher transmission fluid pressure when engaging reverse. 

Rear diff to subframe bushings are probably shot.

GD

Good call on the high cold idle!

 

Want to say thank you for replies. The rear diff bushings to sub frame are mushy. I’ll give update after replacing bushings.