Start with what is installed
Factory System Overview
The GMT900 crew cab can have standard audio, Bose amplification and optional rear-seat entertainment. Start by checking the equipment fitted to the truck. Radio replacement can affect warning sounds, OnStar, the factory amplifier and entertainment connections, so make a retention list before selecting an interface. Keeping an existing feature requires support from both the adapter and the new receiver.
Identify your vehicle and equipment
The model-year range here is 2007–2013, including the new-body 2007 truck sometimes called 2007.5. It does not cover the older GMT800 Classic sold alongside it. Confirm the body and four-door crew-cab configuration; a regular-cab or extended-cab guide is not a substitute for the rear-door and bass planning in this truck.
Radio Upgrade
Single-DIN and suitable double-DIN receivers can be installed with the correct dash kit. Irregularities behind the dash can interfere with wiring and RCA plugs on the upper half of a receiver. Check chassis depth and connector placement; a unit less than 6½ inches deep is an option to investigate, not a guarantee that every short radio fits.
Use a panel tool and 7mm socket/ratchet for radio access, keeping removed trim and hardware organized. Standard audio needs an interface that retains warning chimes and applicable OnStar, with the required turn-signal relay considered. Bose requires an interface compatible with its amplifier if the amplifier is staying. Trucks with rear-seat entertainment need a separate retention connection to a compatible receiver audio/video output. Verify steering-wheel-control support independently.
Speaker Locations and Sizes
Shop Speaker Sizes
Choose the documented location and size, then verify the individual product.
Front doors • 5¼, 6½ or 6¾ inches
5¼-inch Coaxial Speakers6½-inch Coaxial SpeakersBrowse Speakers • verify 6¾-inch fitConfirm brackets, depth, impedance and the retained amplifier. A collection is not a direct-fit guarantee.
Rear doors • 5¼, 6½ or 6¾ inches
5¼-inch Coaxial Speakers6½-inch Coaxial SpeakersBrowse Speakers • verify 6¾-inch fitConfirm brackets, depth, impedance and the retained amplifier. A collection is not a direct-fit guarantee.
Bose front pillars • tweeters
Car TweetersConfirm brackets, depth, impedance and the retained amplifier. A collection is not a direct-fit guarantee.
Nominal size is only a starting point. Confirm exact basket dimensions, mounting, wiring, crossover and amplifier compatibility. Coaxial speakers, midranges and subwoofers are not interchangeable. There is no dedicated 6¾-inch collection linked here; check actual product dimensions in the general speaker collection.
Front doors
The factory basket is closest to 6¾ inches, but aftermarket speakers still require adapter plates. The documented alternatives are 6¾, 6½ and 5¼ inches. Standard front speakers are 4-ohm units. Bose uses low-impedance speakers; substituting ordinary 4-ohm units while retaining that amplifier can reduce volume. Match the replacement to the retained or new amplifier rather than shopping on diameter alone.
Rear doors
The same documented replacement size choices apply to the rear doors: 6¾, 6½ and 5¼ inches, with the correct brackets. Check depth, mounting shape and wiring on the actual truck. Full-range replacements are useful when rear passengers need treble as well as midrange; a midrange-only driver is not an interchangeable full-range replacement.
Front-pillar tweeters, if equipped
Bose-equipped trucks have tweeters in the A-pillars. Removal is relatively accessible, but the replacement requires secure mounting and appropriate wiring; no plug-in harness is specified for this location. A universal bracket or a carefully made mount can support a suitable component tweeter. Keep the crossover and impedance requirements with the rest of the speaker system.
Tools and Preparation
Have a panel tool, 7mm socket and ratchet ready for the radio, plus a small flat-blade screwdriver for the pillar tweeters. Door-panel fasteners and trim vary with the truck; consult the matching disassembly instructions before starting. Gather the required speaker brackets, wiring adapters and secure connectors first.
This overview is for planning, not a substitute for complete vehicle-specific service and disassembly instructions. Protect trim, keep hardware organized and check behind every drilling location. Do not disturb airbag equipment or leave pillar retainers disconnected.
Bass and Amplifier
The Bose console contains a small woofer together with factory amplification. The source does not specify a general-purpose drop-in diameter. If additional bass is the goal, consider a separate amplified subwoofer system instead of treating the factory console driver as a simple swap. The exact enclosure must suit the crew cab and its seat arrangement.
Possible locations include under the rear seat or a purpose-built console enclosure. Measure clearance, check seat travel and preserve access to cabin functions before committing to equipment. If the factory amplifier is bypassed, plan all affected speaker circuits and the new signal source. Adding a larger woofer without a suitable enclosure and amplifier is not a complete bass upgrade.
Installation Checklist
Finish the job with functional checks, not just a listening test.
- Confirm year, body style and factory audio package
- Verify warning chimes and required retention interfaces
- Check receiver depth and rear-plug clearance
- Match speaker size, mounting and electrical load
- Secure all wiring and protect it from moving parts
- Test every speaker before closing the panels
- Check windows, locks and door releases after assembly
- Recheck retained controls and bass-system operation
Keep a record. Save part numbers, interface settings and wiring changes for future service.
Car audio guides, upgrades and installation planning.
