If the transmission is in first gear with a ratio of 2.5:1 and the rear axle has a ratio of 2:1, what is the overall gear ratio?

To determine the overall gear ratio in a manual transmission setup, you multiply the gear ratio of the transmission by the gear ratio of the rear axle. In this case, the transmission is in first gear with a ratio of 2.5:1, and the rear axle has a ratio of 2:1.

Calculating this, you take the transmission ratio of 2.5 and multiply it by the rear axle ratio of 2:

2.5 × 2 = 5.

Thus, the overall gear ratio is 5:1. This means that for every 5 turns of the driveshaft, the wheels turn once, resulting in greater torque at the wheels, which is particularly useful for starting from a stop or climbing steep hills.

This explains why the answer is correct, reflecting the cumulative effect of the gear reductions through both the transmission and the rear axle.