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Diesel Engine Manufacturers Association (DEMA)

A professional association of diesel-engine manufacturers.

Dieseling

A condition in which a carbureted engine continues to run after the ignition is shut off.

Dieseling

A condition in which a gasoline engine continues to run after it has been turned off. It is caused by abnormally high intake manifold pressures, which result from timing that is markedly retarded at idle, a common trait of late-model engines. Also known as run-on.

Diff

An abbreviation for differential.

Differential

The section of the rear-axle assembly that provides three functions.

Differential

A drivetrain, or powertrain component that splits the power transmitted to each drive wheel. By using a differential, when a vehicle goes around a corner, the wheel on the outside is allowed to spin faster than the wheel on the inside, which prevents excessive tire wear. Also known as a rear end or third member

Differential Action

An operational situation where one driving wheel can rotate at a slower speed than the opposite driving wheel.

Differential Assembly

The mechanism that relates to front- or rear -driving axles that permits unequal travel distances and speeds between the vehicle's driving wheels.

Differential Case

The housing of the differential that contains the side and pinion gears and the pinion shaft, and also serves as a mounting place for the ring gear.

Differential Drive Gear

A large, circular helical gear that is driven by the transaxle pinion gear and shaft and that drives the differential assembly.

Differential Housing

Also known as rear-axle housing. A cast iron assembly that houses the differential unit and the drive axles.

Differential Housing

See axle housing.

Differential Lock

A toggle or push-pull type air switch that locks together the rear axles of a tractor so they pull as one for off-the-road operation.

Differential Pinion Gears

Small, beveled gears located on the differential pinion shaft.

Differential Pinion Shaft

A short shaft locked to the differential case. This shaft supports the differential pinion gears.

Differential Pressure Valve

A device that maintains a constant pressure to fuel injectors.

Differential Side Gear

The gears that are internally splined to the axle shafts, which are driven by the pinion gears.

Diffusion Muffler

An exhaust system product that uses diffuser plates to muffle engine sound. These plates split up the sound--or diffuse it--so the sound follows many different paths. You can make this kind of muffler louder--and reduce backpressure--by adding plates. Conversely, you can make it quieter--and increase backpressure--by removing them. Some diffuser mufflers also use absorption material to reduce decibel levels even further. See also muffler, absorption muffler and cancellation muffler.

Dig Out

To accelerate suddenly, as in the start of a race.

Digger

A dragster.