Downgrade 06.15.00 Baseband to 05.13.04 with Redsn0w 0.9.14b2 (Video Tutorial)
This is a video tutorial that will walk you through downgrading your iPhone 3G/3Gs from the iPad baseband 06.15.00 to 05.13.04 which is another Ultrasn0w compatible baseband that will allow you to unlock and use your GPS capabilities. It is very important that if you have a 3Gs and it was manufactured on or after the 35th week of 2011 you SHOULD NOT install the iPad baseband. Doing so will permanently brick your cell radio. You can tell when your device was manufactured by looking at the 3rd, 4th and 5th digits of your phone's serial. The 3rd digit is the last number of the year and the 3rd and 4th together are the week. "135" indicates a device was manufactured on the 35th week of 2011, any device on or after this serial should not use this tutorial.