[G3 General] O29C:
EDIT: Clearly now that there are custom ROMs, this will be less likely an issue. But [MENTION=3527587]icheyne[/MENTION] pointed out a good method that will work on most ROMs I believe, since it uses Android's default testing menu.

For those seeking a permanent solution, you WILL need root.

Currently no permanent solution on LG Stock Lollipop.

Here is some information about my situation:

-Currently on Fido Network in Canada (LTE Band 7 [2600 MHz])

-I have achieved LTE speeds of 31mbps (Down) and 25mbps (Up).

-I am rooted, but it should work without root access.

-Firmware is stock V10h-TWN-XX

-Network mode only shows GSM / WCDMA

Before you begin, this is what you need:

-An LTE micro sim.

-Do some research on which LTE bands your network uses and if your variant has the ability to use that band.

-Correct LTE APN settings for your mobile carrier. Make sure it is LTE APN, my carrier has two separate ones (Regular, LTE).

-Mobile Network does NOT have to be turned off (You can keep data on during all of this).

-With Mobile Network on, go into Settings -> About Phone -> Network and remember what is written under "Mobile network type".

-Make sure you are in a location that has decent LTE connection.

METHOD FOR LG STOCK LOLLIPOP

1) Open up your Dialer, and type in the following to enter LG's Hidden Menu: "3845*#855#" for D855 (If your model is not listed, please do Google it!)

"3845*#850#" for D850

"3845*#851#" for D851

"3845*#852#" for D852

2) Go down and select "LTE-Only" and go into "Modem Settings"

3) Now select "RAT Selection" and click on "GSM/WCDMA/LTE auto"

4) Without rebooting, the data icon switched from "H" / "3G" to "4G" for the first time (Turn on Mobile Network if you haven't already)

5) Now go into Settings -> About Phone -> Network and under "Mobile network type" it should have "LTE" instead of what you had before

Currently no permanent solution, each time you reboot, switch to 2G/3G, or go into "Mobile Networks" menu, you will lose LTE

But it's okay, redoing steps 1 to 3 will get LTE back once again. Tedious, but at least it works :D

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QUICK METHOD (Working for all Jelly Bean ROMs & some Lollipop ROMs) (Thanks to [MENTION=3527587]icheyne[/MENTION])

1) Go into Dialer -> Dial *#*#4636#*#* -> Phone Information

2) Scroll down to "Set preferred network type:" and click on the pull-down menu

3) Select what type of setting you want, I personally keep it on "LTE/GSM/WCDMA"

4) Select "LTE-Only" and go into "Modem Settings"

5) Without rebooting, the data icon switched from "H" / "3G" to "4G" for the first time (Turn on Mobile Network if you haven't already)

6) Now go into Settings -> About Phone -> Network and under "Mobile network type" it should have "LTE" instead of what you had before

7) [ROOT][Permanent LTE] For myself, I used a root explorer (ES File Explorer) and go into "/system/app" and delete (or move) LteConfigs.apk and LteConfigs.odex. Now you should be able to go into the "Mobile network" menu and it should have the "GSM/WCDMA/LTE auto" setting. Thus making LTE a permanent option.

Those without root access will lose LTE if they restart, switch to 2G/3G, or try to go into the "Mobile network" menu.

If you have any questions, please leave a reply. Hope this helped.

If anyone who cannot get this to work, please post with your details (firmware, carrier, LTE band, etc...).