Sound like you either have the end point adjustments set incorrectly, or the servo horn is not centered correctly. The noise you are hearing is the servo reaching maximum throw, but the wheel / tie rod is not letting it, thuss the grinding sound.
Take off the servo horn & reset the servo (on controller) to the middle. Re-install the servo horn (check instructions - attach at slight angle on TC4). Once installed, re-check the wheel travel L & R, and adjust as necessary for maximum turning without binding. Also, if you controller has sub trim option, use that to center the servo by eye, and then the steering trim to fine tune.
If the above does not work, you may have stripped the gears in the servo, and it would need to be replaced. If you are not 100%, take it to your LHS and have them take a look at it. If you do need to replace the servo, upgrade to a metal gear servo, if it is your budget.
Hope this helps.
Retired from RC....
Quantum - St. Croix - Bass Pro Shops - XPS - Rapala