Fixed Side Quarter Glass on the Coupe Versus the Roadster
Replacing the rear vent glass on this sports car requires knowing exactly which body style sits in your driveway. The fixed rear side windows exist strictly on the 3-door Coupe liftback. If you own the Roadster convertible, your car has solid rear quarter pillars made entirely of bodywork, meaning there is no side vent glass to replace. For Coupe owners, the side quarter window sits directly aft of the frameless door glass, acting as a stationary structural panel bonded directly to the unibody frame.
The original factory units correspond to base part numbers 8J8 845 299 (and variants such as 8J8 845 299 B) for the driver side, and 8J8 845 300 (including 8J8 845 300 B) for the passenger side. On the Mk2 Type 8J body, these stationary panels are manufactured from green-tinted, AS2-rated tempered safety glass. They contain no internal motors, hinges, or sliding channels, but their relationship with the vehicle's tight cabin airflow is critical.
Integrated Vulcanized Mouldings and Door Seal Tolerances
Unlike windows that sit in a loose rubber pull-cord channel, each Type 8J rear quarter window features an outer encapsulation seal that is vulcanized directly to the perimeter of the glass at the factory. If the rubber trim surrounding the window cracks, splits, or sustains damage, the moulding cannot be peeled off and swapped on its own; the entire glass assembly must be replaced to restore the seal.
Because the TT Coupe utilizes frameless front doors, the door glass seals directly against the B-pillar weatherstrip immediately adjacent to the leading vertical edge of this quarter panel. When I travel directly to your home or office across Toronto and the GTA to replace this panel on-site, I pay close attention to this joint. If the replacement quarter glass does not match the subtle compound curve of the Type 8J roofline, the trailing edge of the door window will fail to compress against the B-pillar seal correctly, resulting in wind whistle at highway speeds.
Quarter Glass Component Specifications
| Component Feature | Mk2 Coupe Specification |
|---|---|
| Glass Material | AS2 Tempered Safety Glass (Solar Green Tint) |
| Left Side OEM Base Reference | 8J8 845 299 / 8J8 845 299 B |
| Right Side OEM Base Reference | 8J8 845 300 / 8J8 845 300 B |
| Mounting Style | Urethane adhesive bonded to pinch-weld |
| Exterior Surround | Integrated pre-bonded perimeter encapsulation |
Post-Installation Quality Checklist for the Owner
Once your new rear quarter glass is set, take a few minutes to inspect how the panel integrates with the surrounding Audi bodywork:
- B-Pillar Edge Alignment: Close the frameless front door and ensure the door glass seats flush against the vertical seal right at the leading border of the quarter window.
- Encapsulation Contact: Look along the perimeter of the pre-moulded rubber outer edge to verify it lies completely flat against the painted quarter panel without puckering or lifting.
- Exterior Flushness: Check down the beltline of the car to confirm the glass surface sits on the same plane as the surrounding metal rather than sunken or protruding outward.
- C-Pillar Trim Seating: From inside the hatch area, confirm the interior C-pillar trim and lower quarter plastics sit fully pressed back into their retaining clips with no uneven gaps.
- Moisture Check: Inspect the rear trunk floor and lower battery well area after the next heavy rain to verify the bond line is completely watertight along the unibody channel.
