* Complete Transmission Failure: This is the most probable cause. The loud noise indicates internal damage within the transmission. The speedometer malfunction and backward coasting suggest a loss of connection between the engine and the wheels, which is a classic sign of a broken transmission.
* Broken Driveshaft: While less likely given the other symptoms, a severely damaged or broken driveshaft could also cause these issues. However, the loud noise points more strongly towards a transmission failure.
* Differential Failure: A severely damaged differential could lead to similar symptoms, particularly the inability to move and unusual behavior of the speedometer.
Do NOT attempt to drive the car. Trying to start it or put it in gear could cause further damage and potentially injure yourself or others. The loud noise is a warning sign that something is seriously wrong.
What you should do:
1. Call a tow truck: Get your Ford Focus towed to a reputable mechanic or transmission specialist. Do not attempt to drive it.
2. Describe the problem clearly: When you call the tow truck and the mechanic, describe *all* the symptoms you've experienced.
3. Prepare for significant repair costs: Transmission repair or replacement is expensive. Be prepared for a substantial bill, potentially exceeding the value of the car depending on its age and condition.
It's crucial to get this diagnosed and repaired by a professional immediately. Driving the car in its current condition will almost certainly lead to even more extensive and costly damage.
