The simplest answer to the difference between transmission fluid and gear oil is in the purpose for which they are designed. Transmission fluid is engineered to work with automatic transmissions, whereas gear oil is typically intended to work with manual-type gear boxes. However, for a comprehensive understanding of the two fluids, the properties demanded of them and how they differ, we must first explore the key differences between transmissions and gearboxes.
While both pieces of equipment are required to perform the same role of enabling gears to change and control the force, speed, and direction of a vehicle, they achieve their own results using different methods and therefore need different supporting fluids for operation.
Automatic transmissions work in a system that involves multiple gears switching automatically in answer to the different demands of an engine. Gears within an automatic transmission are usually far smaller and greater in number than those contained in a manual system. For effective operations, transmission fluid must not only lubricate but transfer power from the vehicle’s oil pump to its clutches, the machinery that controls gear movement.
Key properties of transmission fluid
Essentially, transmission fluid is a hydraulic oil and an exceptionally thin one. To lubricate the systems delicate components, it must have a low viscosity so it can flow freely transferring power from the vehicle engine to its transmission.
Transmission oil contains detergent to ensure no build-up of debris occurs in channels between parts that might negatively affect operation. It must also have heat-resistant properties as it is required to act as a coolant, transferring heat away from working parts when friction occurs. With a much lower boiling point than gear oil, it typically needs additives to increase its lifespan.
Transmission fluid has also been designed for anti-foaming capabilities, keeping unwanted air out of the lubricant, so it doesn’t interfere with force being transferred.
Manual gearbox operations are based on a system that features two individual shafts and gears that work together when the user interacts with a gearstick and clutch, and because of this, manual systems generate a lot of heat, force and friction. To answer these issues, gear oil has to be capable of making these transitions between gears as smooth and seamless as possible, preventing parts becoming damaged as they shift between positions.
Important qualities of gear fluid
Gear oil is far thicker than standard motor oil. With a high viscosity, the oil can make sure the connected gears are always lubricated and keep them cushioned against the shock and sudden impact when they interact.
As manual gearboxes generate an increased amount of friction, they also create a great deal of heat, so gear oil is engineered to withstand exceptionally high temperatures and safely transfer the heat away from the gearbox. The oil must also be able to operate effectively under extreme pressure, so today’s products offered by manufacturers like Fuchs and Mobil often contain specially formulated additives to deliver improved performance and greater oil stability.