Which factor contributes to excessive noise from the rear axle during acceleration?

Worn axle splines are a significant factor that contributes to excessive noise from the rear axle during acceleration. The axle spline refers to the machined surface on the axle in which the splines engage with the wheel hub connections. When these splines wear down, they can create gaps and improper alignments, leading to slippage and unintended movement within the axle assembly. This condition can generate additional noise due to the friction and impact as components that are no longer snugly fitting together interact during the mechanical operation of the vehicle. The noise is often more pronounced during acceleration when the forces on the axle are increased.

In contrast, while incorrect air pressure, cold weather conditions, and under-inflated tires may contribute to other types of handling or ride quality issues, they do not directly affect the mechanical integrity or assembly of the rear axle itself. Such issues are more related to tire performance and vehicle handling rather than the specific noise generated from the rear axle assembly.