What is low pitched vibrational sound when stopped in gear? It stops in N or P. on 2006 Toyota Tundra

When I put it in neutral or park the sound quits. It appears to be from transmission since it stops making vibrating sound. Any advice or solutions.

Asked by for the 2006 Toyota Tundra
1 answer 2 comments
Possible motor or trans mont
Thanks for reply. Found the problem. Bolt on skid plate missing. Enough to cause vibration.