Drivetrain Loss Calculator
Calculate drivetrain power loss between crank and wheel horsepower.
Drivetrain loss is the power consumed by the transmission, driveshaft, and differential before it reaches the wheels. This calculator finds the loss in both horsepower and percentage from your crank and wheel figures.
Drivetrain Loss Formula
How to Use This Calculator
- Enter crank horsepower (advertised or engine-dyno figure).
- Enter wheel horsepower from the chassis dyno.
- Read the loss in HP and percent.
Worked Example
Where the Power Goes
Drivetrain loss isn't wasted to a single component — it's spread across the transmission gears, torque converter (on automatics), driveshaft, differential, axle bearings, and even the energy spent spinning those parts up. Friction and fluid drag turn a slice of engine power into heat before it ever reaches the pavement. That's why wheel horsepower is always lower than the crank figure manufacturers advertise.
Typical Loss Percentages
As a rule of thumb: front-wheel drive loses about 10–12%, rear-wheel drive 15–17%, and all-wheel drive 20–25%. Automatics generally lose a bit more than manuals due to the torque converter. These are estimates — actual loss varies with gear oil, tire size, temperature, and the specific dyno, so two measurements of the same car can differ by several percent.
Loss for a 350 HP Engine
| Drivetrain | Loss % | Wheel HP |
|---|---|---|
| FWD | 11% | 312 |
| RWD | 15% | 298 |
| AWD | 23% | 270 |
Frequently Asked Questions
It's the power absorbed by the transmission, driveshaft, and differential as it travels from the engine to the wheels, typically 10–25% depending on layout.
Automatics usually lose a few percent more than manuals because of the torque converter and pump, though modern automatics have narrowed the gap.
AWD has extra components — a transfer case and additional differentials — plus more rotating mass, so it absorbs more power than FWD or RWD.
It's a starting estimate for RWD. Real loss varies with drivetrain design, condition, temperature, and even the dyno used, so treat it as approximate.
Somewhat — with efficient gear oils, lighter components, and good maintenance — but it can never be eliminated, since friction is unavoidable.