From another forum. If you google the exact wording, you may be able to figure out where this post came from and download the unlocked image file for 2011.40. If you can't, just think of deviloid. If you still have trouble, PM me and I'll send you the link to the torrent where you can download the unlocked image.
"(Unlocked IMG Instructions)
Use either Part A or Part B depending on your choice:
Part A – Internal Memory
1. Connect your device to the computer.
2. Go into the Nuvi files and backup the file named “gmapprom.img” to your computer.
3. Delete the “gmapprom.img” file from the device.
4. Copy the unlocked “gmapprom.img” file that you downloaded into the device.
5. Restart your device and check your map info via : Tools>Settings>Map>Map Info.
Part B – SD Card
1. Get a 2GB SD card (NOT SDHC) and format it FAT or FAT32
2. Create a folder on the memory card called “Garmin”
3. Copy the downloaded IMG file into the Garmin folder on your SD card.
4. Make sure the IMG file is named “gmapsupp.img” on the SD card.
5. Insert the SD card into your Garmin GPS, and browse to your map information on your Garmin GPS and you should see the new maps selected. This can be found on the device via : Tools>Settings>Map>Map Info. (Note: The SD card must remain in your device if you want to use the maps.)
Why is the file name important?
This must be done because this is not the primary mapset as it is being used from the SD card. The primary mapset is the one on the GPS’s internal memory."