833 trany noise

I just replaced the auto. trany in my 84 pickup with a used 833 overdrive 4 speed.
When i started the truck every thing sounded good untill i let off the clutch petal and a light thumping noise started comeing from the trany. again i pushed in the clutch petal and the noise is gone. Can anyone help me pin point the worn or broken part that is causing this noise

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tschmidt

i pulled it apart its the pinion bearing
see ya