Demarsico

Hello everyone. My first time here. I have a 2021 Sierra AT4 with the 6.2L. I have started to notice a noise when towing our boat that weighs about 6,000lbs. Several times during the trip to and from the lake I hear a rumbling sound that last like 2-4 sec. almost sounds like it can be a jake brake or hitting rumble strips on road. I hit no strips. I can’t recall if it happens on downshift or what. But it does concern me. I drove home from work today with our towing and put it in tow haul mode. It made the noise 3 times in 45 min drive. Any ideas what I’m dealing with? Would it be a bad clutch issue or is this normal? I do have the performance GM installed exhaust and performance GM installed air intake. I called dealer today and they said bring it by and they MIGHT have time to get to it next week. I planned to hit the lake this weekend for Labor Day. Thanks.