Well I let my friend drive my car for about 2 minutes and of course something bad happens. He didn't wait the 1 extra second before the car was fully in "reverse" and gave it gas too soon. The car gave a little jolt then fully engaged. Now a few days later the tranny is making a whining/whirring sound. Kinda like rocks are stuck in the tires. It shifts perfectly fine but I'm hearing a lot more road noise than I used to. Torque converter Any suggestions on what it could be and how much it would cost to fix? Last time I let a friend take my car out for a spin. Car is a 94 530ia.