HOW TRANSMISSION FLUID WORKS IN MANUAL TRANSMISSION VEHICLES
In manual transmission systems, transmission fluid is primarily used to prevent overheating and the premature wear of gears. The transmission fluid also keeps the gears lubricated and at cool operating temperatures.
The type of transmission fluid used in manual transmission systems will largely vary depending on the make, model, and specifications outlined in the vehicle owner's manual. Manual transmissions may use manual gear oil, or transmission fluid specific to each vehicle make and model.
If you have a manual transmission system you want to keep an eye out for contaminated transmission fluid, and specifically transmission fluid that appears to contain any shards of metal from worn bearings or synchronizers. Transmission fluid runs between all the gears in your manual transmission and running metal-laden fluid through metal gears can end up causing untimely wear.
Another thing to look out for is a transmission fluid leak. While the transmission fluid in manual transmission vehicles doesn't tend to naturally break down on its own, loose parts or impact from road debris can cause leaks and low fluid levels.