I have recently upgraded my internet connection to LTE replacing an old USB dongle with the E3272 from Huawei. My router is a Tp-Link TL-WR1043N/ND v1 flashed with Gargoyle firmware 1.6.2.
First lession: seems that Gargoyle 1.7.0 does not work with the new USB key. I Tried many times but seems related to the modem driver.
So, first problem: Huawei E3272 HiLink work as a network card, not like a fake cd-rom drive like many others usb dongles.
To get rid of this i had to download a different firmware from here and i have to choose a FW version beginning with 21 (that means no HiLink mode) and ending with 00 (that means unbranded).
The fast way to load the new firmware on the USB dongle is to use the executable file in the downloaded archive (means usb dongle connected to a windows PC).
After patched the dongle it's time to make a little bit patch in the router configuration. So enable SSH access in the web interface of the router, connect with an SSH client (putty like), insert login data (user: root, password: the same you used in web panel).
Now you have to bind the modem driver to the HW id of your USB dongle. To do so type:
Look for vendor and product ID of the dongle (in my case was 12d1 and 1506) and place the line below (modified with the correct numbers) in the /etc/rc.local (es: vi /etc/rc.local):
echo '12d1 1506 ff' > /sys/bus/usb-serial/drivers/option1/new_id
If you done well, you can type reboot to reset router and you should see the 3G option in the web interface of Gargoyle.
Fell free to contact me for any question (see home page), but I am not an expert on embed linux systems.