So I wanted to add an AUX input on the factory radio. I was going to do this on the 99 but I never got around to it. I figured as the front of this one is broke and the CD player skips it would be a good test. Never liked the FM modulators as they degrade the sound and I travel a lot which makes it hard to keep a clear channel. If you are in one area and can find an empty station that might work for you. This is still cheaper and doesn't require extra power.
I found some instructions over here using Radio Shack part# 274-0246.
As Radio Shack has been closing stores all over the place, it might be easier to get them online, here is a link to a similar jack on amazon. http://amzn.to/2q8LLhS
http://www.gmfullsize.com/forum/showthr ... ?p=3315388
Here are the wires that you need to attach to after removing the bottom of the radio.
I used some CAT5 wire that I had laying around, removed 3 strands as you need 5 wires if you still want the CD player to work when you remove the 3.5mm male-male headphone cable. Note: In this picture the orange and white/orange are reversed.
After removing the face, you can see where it has to be trimmed for the jack to fit. You won't be using the threaded ring that comes with the jack.
Here it is trimmed. 16/64th drill bit for the hole.
PCB board had to be trimmed as well, here it is trimmed and the jack installed.
Hot glue behind jack to prevent it being pushed back when plug is inserted.
Wires attached and working!
Damn it, I didn't get a picture of the radio from the front, will do that soon.
Edit: Here it is from the front.
If you are powering/charging your connected device(BT adapter/phone/tablet) from the vehicle, you may also need some ground loop isolation.
I bought a ground loop isolator from Radioshack as it was local and on sale. However to reduce wiring connections here is one that already has a 3.5mm plug and jack on it to simplify the wiring. https://amzn.to/2Ilsfat
You could also install these inside the head unit/radio so there wouldn't be any requirement to have them hanging around. You could also make your own using the transformers from old computer modems if you happen to have some around.
If you are looking for a double DIN upgrade, Metro makes a kit now:
Without the wiring harness https://amzn.to/332TXj4
With the wiring harness and antenna adapter https://amzn.to/33d6EYR
If you want to do away with the radio all together and use your own bluetooth receiver/amp see this post by Wimptech: $25 Bluetooth Sound System
While this has served me well, and is still working as intended, I really like having navigation/bluetooth built-in as it is with my other vehicles.
My future plan is to go with the double DIN metra kit Double DIN Install - Alpine ILX-207 - Metra Double DIN kit