Transfer case and differential fluid replacement are recommended for several reasons. The main one is to maintain the performance and durability of the transfer case itself as well as the differential. Here are some specific reasons:

Lubrication: Like any fluid in a mechanical system, the fluid ensures lubrication of the transfer case’s internal components. This reduces wear and ensures smoother operation. The components inside these are made of metal and, over time, will accumulate some metal filings, which can then prematurely damage the differential or the transfer case.

Cooling: The fluid also helps dissipate the heat generated by transfer case operation. Excessive heat can cause damage to internal components.

Corrosion protection: The fluid can help protect internal metal parts from corrosion, particularly if the vehicle is used in harsh conditions such as off-road driving, track use, or damp environments.

Performance maintenance: Regular replacement of the transfer case or differential fluid in accordance with the manufacturer’s recommendations ensures that the transfer case operates at its best, which can contribute to better traction and stability, especially in difficult driving conditions.

Failure prevention: Worn-out or contaminated fluid can lead to operating problems or even complete failure if fluid levels are too low or if the fluid is of poor quality.

In short, regular replacement of transfer case and differential fluids is an important part of your vehicle’s preventive maintenance, aimed at ensuring long-term performance, durability, and reliability.