"Putt putt" sound from engine.

[TDot]

I have recently noticed a low tone, low volume "putt putt" sound coming from the engine only when I'm in drive or reverse (if you used your knuckle and knocked on a solid old piece of wood as fast and light as you could that would be the best way to describe the sound) . The sound is not present when I'm in park or neutral...if it is present it's negligible. It seems to be coming from the back of the engine, but I can't be 100% certain. Any ideas at all?

[EdBwoy]

TDot, is it possible for you to record this sound?
Oil level good and all?

[TDot]

I'll see what I can do.

The dealer is said they traced it down to the right cat. Seems odd that the combs going bad has perfect synced timing. I would think something like that would have random timing sounds. He said it's not something that needs to be replaced now, but to be prepared. I think he might have been paying attention to something else. I'll see if I can get a clear recording, something tells me it'll be buried in engine noise.