2020 GMC Sierra 2500HD: Rear sliding window leak
Common wear/failure (not a recall)
Symptoms
Owners of the 2020 Sierra 2500HD report: rear sliding window leak. CarComplaints.com lists 2 owner complaints, average mileage 29,050 miles.
NHTSA has 1 owner complaints for the 2020 Sierra 2500HD in this area. Examples:
- NHTSA complaint ODI #11701143 (filed 11/24/2025): “The rear defroster massively overheated. it started heavily smoking and eventually exploded the rear windows. only warning sign was the smoke which we noticed quickly because the windows were up. had the windows been down we might not have noticed before a fir…”
Likely causes
Sources do not establish a single root cause; diagnosis is needed. Owner-reported fixes are listed below.
Fix, in plain English
Most common owner-reported solutions on CarComplaints.com: replace entire back sliding glass (1 reports) sealant across top of window frame (1 reports). Check for open recalls and extended warranty coverage with a dealer before paying out of pocket.
DIY difficulty: Moderate
Leaks can often be traced with a water test and resealed; glass replacement is a pro job. (Our assessment.)
Cost
CarComplaints.com owners report a typical repair cost of about $1,390 (owner-reported average, not a quote).
Typical parts (search links, no affiliate codes)
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