Have 60k on jeep, vibrations from heatshield in higher rpm 1st and 2nd--not a major issue and can be avoided by quicker shifts--thought someone might have a solution to tightening the shields-- crwood

 

sure its the heat shields, my two lower cats failed on mine at 30K replaced by the dealer, it made a very similar sound to a heat shield vibrating. but sure enough when we banged the cats its replaced the sound. it got progressivly worse when it started it would only do it cold...

not saying this is your issue, just an idea