The 475HB is not a good choice for a TC car. You really need a metal geared servo for this application. It sounds like you probably stripped one of the resin gears in the servo. You can pull the servo apart to check that and if that is the case, a replacement gear set can be purchased at your local hobby shop or mail order shop. Again though, a metal geared servo would be much better for this application as those gears are 12 times stronger.