Reported to dealer & scheduled for service April 21, 2021 & I was advised Tech Service Bulletin was issued but no resolution yet. Scheduled for 5000 miles service this month (August 2021) & advised no resolution yet.

Update from Aug 25, 2021: Dealer advises GM Tech Service Bulletin PIT5778A issued. I am unable to locate this TSB. Dealer Service Tech noted on invoice he found that cause could be by the

"torch condition between the bottom surface of the radiator upper bracket and the top of the radiator tank. Engineering is working on a fix for this concern."

After over an hour on chat with GM Customer Support and getting cut off once, went back to chat and they said can't find a Tech Service Bulletin PIT5778A and I should contact CEM (Customer Experience Manager) at the dealer. Contacted the dealer and waiting for further information. They had another Equinox coming in for service on same issue.

Loud rumbling noise, vibration when backing up and at low forward speeds up 40 mph. Worse at 35-45 mph during slow acceleration. Been to dealer twice and they advise there is a tech service bulletin but no solution. It reportedly is a problem with all 2021 Equinox. Don't understand why GM can't come up with a resolution. They reportedly have identified the problem but not a solution.

Update from Nov 22, 2021: Dealer reports TSB PIT5778A Viibration or Boom at 1300 rpm. Found cause could be by torch (Tourq?) condition between bottom surface of the radiator upper bracket and the top of the radiator upper bracket and top of the radiator tank. Engineering is working on a fix for this concern 1086218 .3