Difference Between Manual Transmission Fluid & Automatic Transmission Fluid

Even though manual transmissions are on the endangered species list, there are still debates about manual vs. automatic transmission fluid. Whether you have a stick or a slush box, you'll want to use the right synthetic transmission fluid to get the most out of it.

The distinctions between manual and automatic transmission fluid come down to what each fluid must accomplish. An automatic transmission is significantly more complex than a manual transmission, even if you aren't an engineer. Similarly, the fluid it takes to function correctly is appropriate.

These are some of the responsibilities of a good manual transmission fluid…

Manual gearbox lubrication requirements aren't simple just because they're less complicated. A good manual transmission fluid must fulfil a number of functions, including...

Enable smooth shifts

A smooth-shifting manual gearbox is the best way to link vehicle and driver. Enthusiasts will not put up with a transmission fluid that obstructs the link.

We have some fluid cross-over here between automatic and manual transmissions. However, depending on the component design, they go about providing seamless changes in different ways.

Synchronisers are standard on most manual transmissions. The synchro, as the name implies, equalizes its speed with that of the engaged gear, allowing for a smooth change. Without it, as they try to mate, the gears spinning at different speeds would collide.

The sleeve and the blocker or synchroniser ring are the two major components of the synchroniser unit. The sleeve advances to the first gear and locks onto the gear engagement teeth, also known as dogs, when the driver selects first gear, for example. When you depress the clutch pedal and select the second gear, the sleeve moves the other way, and you select the second gear in the same way.

The spinning speeds of both the sleeve and the gear must be coordinated before the sleeve can lock onto the gear. The friction between the blocker ring and a cone on the gear's face equalises the speed of the gears, allowing them to mate without colliding. In properly running transmissions, the entire operation happens rapidly and passes unnoticed.

The Viscosity of lubricant plays a major role in shift feel

A high viscosity can impede shifting until the transmission heats up, or it can cause excessively high temperatures during operation. The synchroniser and dog gear may engage too soon if the viscosity is too low, resulting in grinding or harsh shifts and anomalous transmission wear.

Fight wear

Synthetic manual transmission fluid, like automatic transmission fluid, must guard against wear. Manual transmission fluid has a higher viscosity than automatic transmission fluid. This aids the fluid in forming a thick, long-lasting protective coating.

Protect brass synchronisers

Brass is used to make synchrosbecause it is softer than other metals. Some lubricant additives are incompatible with brass and can cause synchros to fail.

Your vehicle's synchros will be protected by correctly formulated manual transmission oil, ensuring they last as long as they should and promoting smooth shifts.

Automatic transmission fluid performs several duties, including...

Act as a hydraulic fluid

To shift gears, automatic transmissions require pressurised fluid. In automatic transmissions, hydraulic fluid is used.

Your vehicle's computer sends an electric signal to the proper transmission solenoid when it's time to shift gears. To engage the correct gear, the solenoid drives fluid through a complex system of passageways in the valve body. To connect the engine to the gearbox output shaft and channel power to the wheels, the fluid squeezes a series of plates together inside a clutch pack.

This all happens instantly in a perfectly operating transmission and is mostly overlooked.

Fluid with a high viscosity, on the other hand, may not flow swiftly enough for crisp, confident movements. Automaticsynthetic transmission fluidhas a lower viscosity than manual transmission fluid for this reason.

Foamy fluid can also fail to perform its function as a hydraulic fluid. Under pressure, the foam bubbles collapse, resulting in elongated or uneven shifts (not to mention gear wear). As a result, foam inhibitors must be present in automatic transmission fluid.

Deliver the correct frictional requirements

The clutch packs are squeezed together by pressurised automatic transmission fluid to engage the correct gears, as previously stated. These clutch packs are made up of bare metal plates and plates with friction material applied to them. To give the driver the optimal driving experience, engagement and disengagement must happen effortlessly.

The frictional qualities of the fluid decide whether this sophisticated choreography of moving metal and fluid produces crisp shifts or requires you to schedule a transmission fluid replacement.

Hence, automatic transmission fluid is specifically engineered to have clear-cut frictional qualities when compared to manual transmission fluid.

Protect gears from wear

Automatic transmissions have a number of sun, planet, and ring gears that need to be lubricated to keep them from wearing down. To avoid metal-to-metal contact and wear, the fluid must produce a durable fluid coating on metal surfaces.

Fight heat

In case you don’t already know, it is heat that is the number one enemy of automatic transmission. It breaks down the fluid chemically (known as oxidation). Sludge and varnish form as fluid breaks down, clogging narrow oil passages and contributing to clutch glazing. Your vehicle may begin to shift harshly, jerk, or hesitate in the near future.

Automatic gearboxes operate hotter than manual transmissions, so the fluid needs to be more heat resistant. One of the reasons why certain automobiles have automatic gearbox fluid coolers is because of this.

Automatic transmission fluid, as you may have guessed, can be used in manual gearboxes in some instances. It new raises another question...

Is it possible to use automatic transmission fluid in a manual transmission?

Yes, as long as the original equipment maker says so. Before pumping ATF into your manual transmission, make sure to check your owner's manual.

In fact, in older units, some manuals may call for gear lubrication or even motor oil.

We should also mention that continuously variable transmissions (CVT), which are becoming increasingly common due to their enhanced economy, use their own fluid. Dual-clutch gearboxes (DCT), which are found in many sports cars, do as well.

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