03 Honda Odyssey "Grinding" Noise - Transmission?

I have an 03 Odyssey, 77K miles. For about the last 3 yrs we get this intermittent grinding/chattering noise from the area just in front of drivers side firewall. Not loud, and usually when we’re going between 35-45 mph. Sometimes I can actually feel a low level vibration on the brake or gas pedal. As is usually the case I can’t duplicate it when I take it in to my mechanic. Other than the noise, there’s no adverse affects. My concern is that it has something to do with the transmission mostly because I’ve read (online, Consumer rpts) that the 01/02 and to some extent the 03 Odysseys had problems with the transmissions failing. There was a recall which installed a 2nd gear cooling line and I’ve had a 4th gear pressure switch replaced. My question is, can I have a trans shop “inspect” my transmission and tell first off it 's that’s where the noise is coming from but more important, if my transmission is “at risk”? My mechanic says if it’s going bad it will start slipping (does not). Do they actually have to “drop the trans” to inspect it and can they assess if it’s good/bad? Yes, I’ve had it serviced regularly.