1999-02 GMC Sierra Extended Cab

1999 GMC Sierra with Extended Cab  (Crutchfield Research Photo)

Overview

GMC’s Sierra is a workhorse, and its toughness is evident by the number of older trucks you still see on the road. This truck may get the job done, but the factory stereo comes up a little short. There are plenty of ways to bring it up-to-date with better sound and features like satellite radio and Bluetooth® to make the Sierra a complete package.

The Sierra's original radio is 3" tall so you can replace it with a 2" tall DIN radio with a mounting kit. (Crutchfield Research Photo)

Replacing the factory radio

Sierras were equipped with GM’s standard AM/FM CD player, which is slightly taller and shallower than most single-DIN aftermarket stereos. It’s easy to get pretty much any single-DIN stereo to fit, because you have over 7" to play with behind the dash. You'll need a mounting kit to trim out the new radio, a wiring harness that allows you to connect your new radio without having to cut the factory wiring, and an adapter that connects the GMC antenna to your new radio. (Crutchfield includes these installation parts free with most orders, along with our step-by-step instructions for your Sierra.)

This truck offered an analog version of OnStar® which is no longer available, so that won't be an issue when replacing your radio. The column-mounted shifter, however, might be. A receiver with a flip-out screen probably isn’t a good idea in this truck because the screen will hit the gearshift  when it opens.

Mounting kit in place, waiting for its single-DIN radio. (Crutchfield Research Photo)

Steering wheel audio controls
Not all Sierras came with steering wheel audio controls, but if yours did, it's relatively easy to keep them. Two companies (PAC and Axxess) make adapters that allow you to connect your Sierra's steering wheel audio controls to a new car stereo. There’s no data wire in this truck, so you’ll tap into the steering wheel controls in the dash. That means either the PAC or Axxess piece will work equally well.

Tools needed: Panel tool 

Shop for car stereos that fit your GMC Sierra 1500

Replacing your factory speakers

The Sierra front door holds a 6-1/2" speaker with an integrated bracket. (Crutchfield Research Photo)

Front doors 
Stock speakers for the front of the Sierra are 6-1/2", a common size with great aftermarket support. You won’t have trouble finding a speaker to fit any musical taste or budget. You can install a 6-1/2" or 5-1/4" speaker using a simple adapter plate for easy installation, and you can also install the slightly larger 6-3/4" speaker if you’re willing to drill some new screw holes.You’ll need wiring harnesses to connect your new speakers. They'll allow you to attach the new speakers to the plugs that connect to the GM factory speakers, and they make it easier to reinstall the factory speakers if you ever sell your truck (Crutchfield includes these mounting brackets and speaker wiring harnesses with every speaker order).

This tweeter is found mounted above the speaker in the front door if you have the less common 6-speaker system. (Crutchfield Research Photo)

Some Sierra are also equipped with tweeters in the doors. These are also easy to remove, and offer a handy mounting spot should you want to add aftermarket units. You’ll have to fashion a mounting plate for the new tweeter.

Tools needed: Panel tool, 7mm SRE

Rear doors/side panels
Many Chevy and GM vehicles use 4"x6" speakers, and this truck is no exception. There are 4"x6" speakers in the rear doors in the 4-door Sierra Extended Cab, or in the rear door and side panel of the 3-door version. Once you’ve removed the body panels to get to these speakers, they’re extremely easy to take out, thanks to their clip-in plates.

Rear doors hold 4"x6" speakers. (Crutchfield Research Photo)

The 3-door Extended Cab truck has a 4"x6" speaker in the rear door and in a rear side panel. (Crutchfield Research Photo)

You have plenty of aftermarket options for upgrading these speakers, including 4"x6" plate speakers, as well as 3-1/2" or 4" speakers which will fit using inexpensive adapter plates. You’ll have to drill new screw holes to accommodate any new rear speakers.

Tools needed: Panel tool, 7mm SRE

Shop for speakers that fit your GMC Sierra 1500

These JL Audio Stealthboxes contain 10" subwoofers and fit under each side of the rear bench seat. (Photo courtesy of JL Audio)

Bass in your Sierra

Nothing but good news here. You’ll find an amazing number of subwoofer options for every body style of this popular truck. If you want bass, you should be able to find a nice enclosure that won’t take up too much space in your Sierra.

You'll find that custom enclosures, like the JL Audio Stealthboxes show here, are the best solution for adding bass without giving up valuable interior space. Custom boxes are built to fit in out-of-the-way places and still let you get the big bass that only 10" or 12" subwoofers can provide.

Other Options

Amps
Being a pickup truck, the Sierra has a noisy cabin. If you really want to hear your music without taxing your speakers, add an amp. There are plenty of inexpensive options that will give you the ability to hear your music loud and clear, especially when paired with some upgraded speakers and some Dynamat in your doors. Mounting options abound; a best bet is under the front or rear seats.

Navigation
The Sierra did not come equipped with navigation from the factory, and in-dash navigation is not realistic due to the limitations of the dash opening. Your best course of action is to use a portable navigation unit, which you can move between vehicles as needed and keep tucked in a storage compartment when not in use.

Security
You can install a security system in this Sierra without a module. If you’re installing a remote start system in this truck, you will need the PLJX immobilizer override, along with a relay to power up the extra ignition circuit. Also, if you want to control the door locks, you'll need two relays if your alarm or remote start system doesn't support 3 wire positive switching locks.

Upgrading your Sierra

Quick & easy
This truck is easy to upgrade, so go ahead and swap out the front speakers and replace the factory stereo with a stereo that puts out more power – the difference in sound quality will be impressive. Your options for an aftermarket stereo are limited to single-DIN units, so spend a little more on a deck that you can upgrade in the future (preamp outputs, Bluetooth functionality, iPod® adapters, etc.).

More bump in your truck
Once you have a new head unit with preamp outputs, expand your system with some amps and a subwoofer. The custom-made enclosures for this truck are amazing – they tuck out of the way, and some come pre-loaded with some of the best subs on the market. Make sure you feed them enough power to really let them achieve their full potential.

Safety, sound and performance
Head unit, speakers, amps and subs – your truck sounds great, now make it more functional. Adding features like a Bluetooth interface keeps you safe on the road, or install a DVD player to turn the bed of your Sierra into your own private movie theater.