Hi, I am new to the forum and hope this is the correct place for this information.
I saw a post relating to the LG 8000 line and the "car kit" no sound issue.
My phone is an LG 8100, but this may work for many others.
The wonderful technician at Verizon told my wife that the phone could not be fixed after she dropped it into a piece of pizza. The sauce went inside the charger connector port and somehow shorted the pins, causing it to go in to car kit mode. This rendered the sound useless, but everything else worked.
Solution: I sprayed CRC QD Electronic cleaner in to the port. I then very carefully used a small pick to clean out the sauce bits. It took several sprayings, but it eventually cleaned all the pins off. This turned off the car kit mode and the phone worked properly.
Moral: Be skeptical of people working for large companies who don't want to help fix one of their products, when they can get you to buy another for more money!