[HTC Vivid, Raider, Velocity] phrotac:
New alternate method below!

Wildchild and Romrix both suggested to create a new google sync account to solve the in call volume issue but that did not work for me. At least, not at first. Not only did I have no contacts, no calendars, etc., I still had low in call volume. I then added my old google sync account so I could back up my contacts but they did not import as a secondary account so I deleted the account from the phone and it told me my settings would also be deleted from google sync. I then reflashed 4.1 beta tweaks build and synced back to my original google sync account to get contacts. While syncing, my phone rang. I answered to discover that my in call volume had fixed itself. After spending a day trying to recreate the low in call volume I was left scratching my head. That's when wmunn said:

Thank you wmunn for pointing that out.

That's when I put it all together and came up with this guide.

These are the steps that worked for me...

Delete your google sync account from your phone (3.6 or 4.1 doesn't matter) so it will delete any stored settings from google sync account (settings are still on phone though) (

extremely

important).

Create a new gmail account and do nothing with it after authorization.

Back up anything you want to keep from internal sdcard.

Boot into recovery by removing battery and NOT through the power menu shortcut. (optional but recommended)

Normal wipes with two additions... Wipe internal sdcard and wipe system (

extremely

important)

Flash your phone with 4.1 ROM from either Homeslice or WildChild (both are experiencing the same problems with in call volume).

Sync to new "virgin" gmail account during setup so it will "virginize" your settings in the phone and get rid of any stored google sync settings (

extremely

important)

Once your phone is completely booted and synced with google, pull your battery and enter recovery (optional but HIGHLY recommended at this stage. The idea is to get as "fresh" of an install as possible).

Reflash your phone with 4.1 ROM and sync with old google sync account.

Set up as normal from here.

Good Luck! Let me know your results ;)

UPDATE: I now know that romrix stumbled across this "fix" back in February. He fixed it by backing up his contacts with SnapPea, creating a new google sync account, syncing to it leaving his old account behind, and restoring his contacts with SnapPea. I did not know this when I created this thread. Sorry Romrix.

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Alternate method:

The above worked for me until I flashed a new WCX Beta ROM and my volume was gone again. This time, no matter how many times I tried the above steps, my volume just would not come back. So, I decided to try something new. This is what worked this time:

I deleted my google sync account from my phone.

I relocked my bootloader using fastboot and my unlock.bin token.

I ran the RUU from my computer and let it flash my phone back to stock 3.6.

I skipped through the setup steps (do not log in to google sync at this time).

I unlocked my bootloader using fastboot and my unlock.bin token.

I rebooted into bootloader and flashed recovery and kernel using fastboot making sure to use the latest WCX Beta ROM kernel.

I booted into recovery (WCX preferred) and wiped everything except for boot and sdcard (do wipe internal sdcard).

I then flashed the latest WCX Beta ROM.

I completed setup but did not log in to google sync yet.

I tested in call volume. It was good.

I logged in to google sync and made another test call. No change to in call volume.

Good luck again!