This is a revision to the previous methods found on the unlockr or xda on how to gain a temp root through the gingerbread update on the T-mobile G2. The latest official Gingerbread update for the T-Mobile G2  seemed to have killed the ability to gain root access. So the only way to get root access is to downgrade the software, by doing So it can allow you to do a perma root and install custom roms cooked up on xda or any other place, or allow you to over clock your G2.I would like to say thanks though to the people who discovered this and thanks to the unlockr for re-posting this.

*****PROCEED AT YOUR OWN RISK, I TAKE NO RESPONSIBILITY IN YOU BRICKING YOUR DEVICE******

I. Setup ADB

1. (I will post the original article for those of you that are fresh to setting up ADB, i found it on the unlockr) Head to http://goo.gl/bXQhQ (the unlockr) for beginners. or to the direct video http://goo.gl/82iDf (youtube)  , follow it, and come back here once you can see a serial number at the end of that procedure.

II. Gain Temporary Root

1. Open settings then click applications, development, and make sure that usb debugging is check marked. Now Plug in your device via USB if it isn’t plugged in already.

2. Download the latest version of Fre3vo (link down below) and then copy Fre3vo to the same folder that adb is located in which should be: C:\AndroidSDK\Tools or C:\AndroidSDK\Platform-tools

http://goo.gl/1wTbh

3. Download the Misc Version file (link down below) and then place the Misc Version file in the same folder that adb is located in which should be: C:\AndroidSDK\Tools or C:\AndroidSDK\Platform-tools

http://goo.gl/M81L4

4. Open the command prompt on your pc by clicking on the Start menu or hitting the windows key and typing cmd and hitting enter in the search box.

5. MAKE SURE PHONE IS SECURELY CONNECTED. Then type the following lines of code into command prompt (or copy what i have typed below one line at a time and then right click in the command prompt and choose paste) after each line hit enter

(the first line is to access the folder that has ADB in it)

cd c:\androidsdk\tools\  *or*  cd c:\androidsdk\platform-tools

adb push fre3vo /data/local/tmp

adb push misc_version /data/local/tmp/

adb shell chmod 777 /data/local/tmp/fre3vo

adb shell chmod 777 /data/local/tmp/misc_version

adb shell /data/local/tmp/fre3vo -debug

^ {you can enter this last line of code but some people experience a hang or freeze like i did, optionally try the following lines instead; only one at a time though let the line run, if you experience a hang or freeze in the command prompt hit ctrl c that will cancel out anything. then type adb reboot to reboot the phone and try another one of the following once it has booted back up. you may have to redo all the previous lines though}

adb shell /data/local/tmp/fre3vo -debug -start FBA90000 -end FFFFFFFF

adb shell /data/local/tmp/fre3vo -debug -start F0000000 -end FFFFFFFF

adb shell /data/local/tmp/fre3vo -debug -start FAA90000 -end FFFFFFFF

adb shell /data/local/tmp/fre3vo -debug -start E0000000 -end EFFFFFFF

5. If one of the following above ^ works it should start scanning and looking for an exploit. Once it finds it, LEAVE THIS COMMAND PROMPT OPEN and head to the next step.

III. Downgrade Misc Version

1. In the command prompt, type the following or copy and past, hitting enter at the end of each line:

adb shell /data/local/tmp/misc_version -s 1.19.531.1

adb shell cd /data/local/tmp

adb shell chmod 777 /data/local/tmp/misc_version

adb shell ./data/local/tmp/misc_version -s 1.19.531.1

adb shell sync

adb shell dd if=/dev/block/mmcblk0p17 bs=1 skip=160 count=10

IV. Downgrade the ROM

1. Download the 2.2 ROM version for the T-Mobile G2  (link down below this paragraph) and then rename it PC10IMG (no need to put .zip as it is already a zip file) now that you have renamed the file copy PC10IMG to the same folder that ADB is located in which should be C:\AndroidSDK\Tools *or* C:\AndroidSDK\Platform-tools

http://goo.gl/cBSzQ  

2. Also your going to need Fastboot.exe (download link below, click the link and scroll down just a little you should see the download).. Move Fastboot.exe to the same folder that ADB is located in which again should be C:\AndroidSDK\Tools *or* C:\AndroidSDK\Platform-tools

http://goo.gl/6vaqP

Leaving the Previous Command Prompt open {Do Not Close Original command prompt}. Open a NEW command prompt and type the following lines hitting enter at the end of each line:

Cd C:\androidsdk\platform-tools\

 
adb reboot bootloader

(your device will reboot into bootloader mode and say fastboot usb on it in red text, wait for it to do that once it says fastboot enter the following command at the prompt)

fastboot oem rebootRUU

(your device will reboot to a black screen with an HTC logo, wait for it to do that, once it does enter the next line)

fastboot flash zip PC10IMG.zip

(your device will begin to flash the original ROM)

WATCH YOUR DEVICE..When it says repeat immediately,Type the following line (it’s the same line as above )

fastboot flash zip PC10IMG.zip

after it says ok you should see a green progress bar. at this point do not close the command prompt (I REPEAT DO NOT CLOSE THE COMMAND PROMPT)..WAIT until the bar is at 100 percent should take anywhere between 5-10 minutes

when the green progress bar is at 100 percent and you are sure that it is done reopen the most recent command prompt (the one that you typed fastboot flash in) and type the following command

fastboot reboot

after doing the previous command the phone should reboot and you should see the familiar tmobile g2 logo as the phone boots back up

CONGRATULATIONS
if you have followed the steps and had success my hat is tipped to you my friend