[G Pad 8.3 General] SLAB_8002:
This walkthrough assumes that you're going to use the stock rooted image, not inject root into your own system image. I've done the root injection, but it was several years ago and it was a good deal more complicated than just using the stock rootedsystem.img.

OK, first things first. Make sure you perform the following steps to gather the tools you'll need:

Install the appropriate drivers.

Download the LG_Root.zip and unzip it in the location of your choice.

Download rootedsystem.img and move it into the folder that you created when you unzipped LG_Root. That way, you should have a folder with adb.exe, send_command.exe, ports.bat, and rootedsystem.img in it (among others).

Next, determine the proper COM port number to use to communicate with your device, and reboot into download mode. Device needs to be powered on and connected to your PC for this step. Alternatively, if you know how to boot into download mode using the volume up button and USB cable, you can boot into download mode and skip steps #3-5.

Open the LG_Root folder, and double-click on ports.bat. It'll open a command prompt window with the output from a reg query. You're looking for the line that has something like "\Device\LGVZANDNETDIAG1". Write down or remember the COM port list on that line. In my case it is "COM3".

Open a command prompt in the same folder where you unzipped LG_Root. If Windows will let you, you can shift-R click in the folder and select "Open command prompt here". In my case, Windows 10 will only let me open PowerShell by that method, so I have to open Command Prompt from the start menu and type "cd C:\Users\<username>\Downloads\LG_Root".

From the command prompt, type

send_command \\.\COM[COLOR="Lime"][Insert COM port number here][/COLOR]

Your command prompt window should display #, which means you are in send command mode.

Type ENTER. Your device will reboot into download mode. You'll know you're in download mode when you see a black screen with Firmware Update up top.

Now, to push the rootedsystem.img to your device and install it.

From the regular command prompt (i.e. NOT in send command mode), type

adb push rootedsystem.img /data/local/tmp

Wait until you see something like 4600 KB/s (3758096384 bytes in 797.736s) and return to the command prompt

Once that's complete, type

send_command \\.\COM3 [COLOR="Lime"]As before, substitute the correct COM port number[/COLOR]

Once you see the # prompt, type

dd if=/data/local/tmp/rootedsystem.img bs=8192 seek=44992 count=458752 of=/dev/block/mmcblk0

The progress bar on your tablet's screen will stay at 0%. The only way you'll know the process is complete is when your computer screen returns to the # prompt. If I remember right, it took about 10-15 minutes for it to complete, so be patient.

At the # prompt, type

LEAVE

Your device will reboot normally, and once you complete all of the necessary steps to set it up you can check to make sure you have SuperSU installed in your app drawer. If you do, you should have root access.

Once your device has rebooted, you've confirmed you have root access, and while still keeping your device connected by USB, type

adb shell rm /data/local/tmp/rootedsystem.img

Let me know if this doesn't work, or if you have issues following it, and I'll see where I screwed up. I've done this 3-4 times, as recently as 3 weeks ago, as a result of tinkering with my device and resetting it, so the method works.