When putting my car in reverse there's a very loud grinding noise then clutch stalls out. Also when driving down the highway there's a rattling sound coming from under the vehicle.
My car has 75000 miles.
My car has a manual transmission.
The rattling noise under the vehicle could be a loose heat shield that could be moving around when the wind is moving fast under the vehicle. For the grinding issue when going in reverse, the reverse gear could have broken teeth causing the gear to grind as it is engaged. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your transmission noises.