I am going to lead you through an install of a navigation radio into a 2008 chevy silverado crewcab ltz with the 6 disc cd radio. This is a bose system. No rear seat entertainment. I am using gm part # 25846421 nav. radio.  You will need a gps antenna, a vss/voice harness, and a navigation disc (25974486)  for the radio that you are installing. Write down the xm ID number channel 0 for future reference. I got the vss/voice harness and the gps antenna from ebay member Tauk.

You will begin by removing the center trim panel around the radio.  I suggest you get some plastic trim tools. Start at the top where the wood and grey plastic meet. The panel is about 3/16 thick. Start prying out and down both sides. The panel is held on with 9 steel spring clips. Be careful as the panel is fragile.

Next, start at the bottom, remove the 8-7mm screws that hold the radio, heater controls and 12v power outlets. There is about six inches of spare wire so you can pull them out to unplug them.  Unplug the 2 wires and the antenna from the radio and set aside.

Next we will install the gps antenna.   First remove the little oval shaped plug on the drivers winshield pillar. It just snaps out. Then remove the 7mm bolt under the cap. Pry the long cover off. There is one spring clip about halfway down the pillar and the bottom is just tucked under the moulding.  Unplug the speaker.  Next pry up the long trim piece that runs along the windshield. It just pops up and hinges towards the windshield. You can support the trim piece with a towel and if you look to the right of center you will see an area where you can just snap the antenna in place. Fish the antenna  wire down to the radio cavity. Reinstall  the trim pieces. now comes the fun part.

You will take the wire  from the vss kit. It will be the one with the brown connector and green wire. Under the dash on the drivers side near the parking brake, you will see a black plastic cover. Remove this cover and you will see a wire terminal box. At the top of the terminal box you will see a clip on each side. Squeeze them together and pull the box towards you. You will see on the bottom a lug on each side. Lift up and gently turn the wire terminal box clockwise so you can see the back.  You will see two blue levers. Looking at it, the one on the right side is where the vss wire is located. It is the green wire with the white tracer. Located in H1 slot. There is another green wire right below it. It is on the right side about halfway up the box. Using a red 3m connector splice the green wire from the vss kit to the green wire with the white tracer. Run this wire back to the radio so that the brown plug is there. You will not use the black and red wires. I cut them off. The rca connector(yellow) is if you want to run rear monitor.

Next the other wire in the kit is the voice wire. If you look right behind the back of the radio cavity, you will see the onstar module. The grey connector plugs in the rear of this module.  It goes in the third slot, right next to the other two plugs that are all ready there. I was able to plug this in by laying on the drivers side and going behind the consel. It is a tight fit, but I used a long pair of pliers to get it into the back and then pushed it in with my hand.  It will only plug in one way.  Feed the black and red wire into the radio cavity as the will go into the black factory plug from the radio.  You will look on the side of the black radio connector and you will see a small grey square pin. Pull this straight out. This will allow you to insert the red wire in the number 4 hole and the black wire in the number 5 hole. This was the order on the kit I got. Make sure the proper color wire goes in the proper pin hole.   If you are looking at the plug as it goes into the radio, they will go in the top row. 4 and 5 positions from the right. there are two open holes. Just push them all the way in in the right position and replace the grey plastic pin. Now tape up you wires so that they are neat. There are now 3 plugs and the gps and regular antenna to plug in.  Reinstall the radio, controls. I would not install the trim plate until you have the radio up and running.  Make sure you have all your wires up and out of the way nice and neat.

Turn on the radio. If you get a bowtie, go on and install the nav. disc and program the radio.  If you get a blue screen and the words theft lock, you will need to go to a dealer with a tech 2 tool. Good luck!!!

This guide is for a 2008 silverado crewcab ltz.  It is for you info only. This may work on other gm models.