Start with what is installed
Factory System Overview
These guides cover the GMT400 Chevrolet and GMC pickups in standard, extended and crew-cab configurations. Speaker access is not identical across those cabs, and rear-pillar trim also changes after 1995. Identify both the cab and the original audio equipment before ordering parts. In 1999, this older body style overlapped with the newer GMT800 Silverado and Sierra; the model year alone is not a reliable parts selector.
Confirm original equipment
Some systems have separate front-door tweeters and a separate CD or cassette unit below the climate controls. Trucks built without rear speakers may not have rear-speaker wiring. Check the actual truck rather than assuming an empty grille means a complete speaker circuit is behind it.
Planning guide, not a fitment guarantee. Match wiring, impedance, adapters, fasteners and removal instructions to the actual vehicle. Photos illustrate selected configurations, not every trim level or every removal step.
Radio Upgrade
A single-DIN receiver is the simpler dashboard upgrade. A double-DIN installation requires the appropriate conversion kit and modification of the support behind the original radio. Confirm the receiver depth and kit procedure before removing or cutting a bracket. The separate factory CD or cassette unit below the climate controls will no longer operate when its original main radio is removed; plan whether to leave it in place or replace it with a suitable storage pocket.
Installation planning
The large dash surround must be handled gently. Disconnect its switch connectors rather than pulling against the wiring, and protect the brittle trim around the steering column. Access can require moving the column shifter; secure the truck against movement and follow the vehicle-specific instructions. Release the radio’s retaining tabs, connect the correct harness and antenna adapter, and test the new receiver before seating the dash surround bottom-first.
Shop Speaker Sizes
Choose a location below, then browse the matching collection.
Front doors • 6.5-inch factory
6.5-inch coaxial speakersCheck depth, adapters and new mounting-hole requirements.
Front doors • alternate 5.25-inch
5.25-inch coaxial speakersA supported replacement option with the correct bracket; not the factory size.
Front doors • equipped tweeters
Car tweetersDiameter is not specified. Custom mounting and crossover matching are required.
Crew rear doors • replacement options
6.5-inch coaxial speakersFactory diameter is not established. Verify 5.25-, 6.5- or 6.75-inch replacements and hardware.
Rear pillars • 4x6-inch factory
4x6-inch coaxial speakersCheck cab-specific trim and wiring. A 4-inch round replacement needs an adapter.
Rear pillars • alternate 4-inch
4-inch coaxial speakersAdapter-dependent alternative, not a direct-fit claim.
These collections are browsing categories, not vehicle-fitment guarantees. Check mounting depth, brackets, wiring, impedance and crossover requirements. Alternate sizes need the specified mounting adaptation. A coaxial speaker is not interchangeable with every component woofer or tweeter.
Speaker Locations
Front doors contain 6.5-inch factory woofers. Their mounting arrangement uses a top spring tab and lower tabs, so an aftermarket driver may require an adapter and new holes rather than dropping directly into the original mount. The door trim, armrest fasteners and sail panel must come off carefully; manual-window versions also have a crank retaining clip. Keep the courtesy-light and switch wiring clear when lifting the panel.
Rear speakers and access
Crew-cab rear-door replacements can use 5.25-, 6.5- or 6.75-inch drivers with the appropriate fitment hardware; the supplied reference does not establish the original diameter. Rear-pillar speakers are 4x6-inch units. On 1995 standard cabs, access starts at the grille; 1996-up standard cabs use interlocking upper/rear trim, while extended and crew cabs also require coordinated trim removal. Do not pry one trapped panel free and break the adjoining pieces.
Tools
For front doors, prepare a panel tool, small flat-blade screwdriver, 9/32-inch socket, ratchet and extension; some replacements require a drill with a 1/8-inch bit. Later standard-cab rear work also calls for 7/32- and 9/16-inch sockets, a Phillips screwdriver and a T47 driver. Extended/crew-cab rear work can require a T50 driver. Match tools and trim instructions to the cab before starting.
Bass and Amplifier
A standard cab has limited depth behind its seat. The source’s planning envelope is approximately 33 inches wide, 17.5 inches high and 6 inches deep at one edge tapering to 3 inches at the other. Measure your own seat travel, jack storage and enclosure clearance rather than treating those numbers as a guaranteed fit. Extended and crew cabs need their own measurements; a compact powered subwoofer can be easier to place than a large box.
Build around the truck
Treat added kick-panel speakers as a custom location, not a factory replacement. Match any component set to its crossover and secure the tweeters with an appropriate fabricated mount. Door treatment can address rattles, but must leave drains, window mechanisms and wiring serviceable. Have security or remote-start integration handled by a qualified installer if it is outside your experience.
Installation Checklist
Complete the system in stages and check it again after reassembly.
- Confirm the year, generation, cab and factory equipment
- Choose a compatible radio kit, harness and antenna adapter
- Check all original functions that need to be retained
- Verify each speaker size, depth, bracket and electrical requirement
- Protect wiring and inspect behind every new mounting hole
- Test each channel and door function before refitting panels
- Secure added bass equipment without obstructing moving parts
- Check final operation after all trim is installed
Keep a record. Save equipment models, interface instructions, wiring changes and tuning settings for future service.
Car audio guides, upgrades and installation planning.
