Unknown. My truck has only about 46,000 miles. We experience heavy rains on the week of 4/8/2024 and i went to go load groceries in the back and saw water coming down the back window. I went straight to the dealer and spoke with tom a manager at gmc. He took me to service and a mechanic came out and said this a common and expensive job. He said i may need anew window replacement. I left and did research on this problem. There seems to be everyone who has a gmc or chevy has this problem. Many people are experiencing rust, mold, etc. This is a major issue. All you hear about mold health isssues. Not any issue that should be over look. Whenthere is water there is mold. This issue probably has been going on longer but due to heavy rain and me going in the back i saw water. This is something that dealers need to fix.