2018 Tesla Model S Transmission & Axle Gear Ratios

Transmission gear ratios

The 2018 Tesla Model S utilizes a single-speed direct drive transmission for each of its electric motors, eliminating the need for complex multi-gear setups found in internal combustion engine vehicles. This simplified design contributes to the instant torque delivery and smooth acceleration characteristic of electric vehicles.

It's important to note that the "ratio" here refers to the overall reduction from the motor to the wheel, incorporating both the transmission gear and the differential ratio into a single final drive ratio. Tesla does not typically provide separate internal transmission ratios as they are integrated into the final drive unit.

Available axle ratios

For the 2018 Tesla Model S, the "axle ratio" is integrated into the final drive unit, which is part of the electric motor assembly. Unlike traditional vehicles with a separate differential, Tesla's powertrain combines these elements. Therefore, there are no separately configurable axle ratios in the traditional sense. The final drive ratio is consistent across different Model S trims for a given year, though it can vary slightly between different motor configurations (e.g., front vs. rear motor in a Dual Motor setup).

How to identify your axle ratio

Identifying the "axle ratio" on a 2018 Tesla Model S is not applicable in the same way as it is for traditional gasoline or diesel vehicles. There isn't a separate axle tag or an RPO sticker with a specific axle code, as the final drive ratio is an inherent part of the electric drive unit itself. If you need to confirm the precise final drive ratio for your vehicle, the best method would be to consult your owner's manual or contact Tesla service directly with your VIN.

Towing vs MPG impact

While the 2018 Tesla Model S is not officially rated for towing in most markets, understanding the impact of gear ratios on performance is still relevant. With an electric vehicle like the Model S, the single, relatively high final drive ratio (~9.73:1) is optimized for a balance of instantaneous acceleration and efficient highway cruising. In traditional vehicles:

• Numerically lower ratio (e.g., 3.08, 3.23): Generally leads to better fuel economy (or, in an EV, potentially better energy efficiency at higher speeds) as the engine/motor operates at lower RPMs at a given road speed. However, it can reduce towing capacity and acceleration.
• Numerically higher ratio (e.g., 3.73, 4.10): Typically provides better towing capability and stronger acceleration from a stop due to increased torque multiplication. The trade-off is often reduced fuel economy (or increased energy consumption) as the engine/motor operates at higher RPMs.

For the Model S, the chosen final drive ratio is a result of Tesla's engineering to provide a compelling blend of thrilling performance and an impressive driving range without the need for multiple gears or selectable axle ratios.

Common issues

Unlike traditional differentials with separate ring and pinion gears, Tesla's integrated drive units are generally very robust. However, some owners have reported rare occurrences that could be likened to "issues" in a traditional drivetrain context:

• Whining or humming noises: While rare, some owners have reported subtle whining or humming noises originating from the drive units, particularly under acceleration or deceleration. This can sometimes be attributed to manufacturing tolerances or, in very rare cases, issues with bearings within the drive unit. If you experience unusual noises, it's best to have a Tesla service center diagnose the issue.
• Bearing wear: Like any rotating mechanical component, the bearings within the electric drive units can, over extended periods and high mileage, experience wear. This is more of a long-term maintenance consideration rather than a common defect. Regular service inspections can help identify potential issues early.

It's important to note that these are not widespread or common issues and Tesla vehicles are known for their reliable electric powertrains.

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