At Belconnen Transmission & Driveline Services we specialise in differential repairs and replacements. If you are experiencing a whirring or grinding sound coming from the rear of your vehicle it could be that you have a differential problem.

The differential is the mechanism that enables the creation of torque (turning force) in the crankshaft before it is distributed through the transmission, to the drive shaft, and then to the wheels. The differential serves to transmit engine power to the wheels while also enabling them to have different rotation speeds. Hence the name 'differential', it can distribute different speeds to wheels especially during a turn.

The pair of driving wheels in a vehicle does not rotate at the same speed during a turn. In situations like this, the wheel on the turning side (inside wheel) rotates slower than its counterpart (outside wheel). This is made possible with the help of the rear differential’s side gears and spiders. To put it simply, this mechanism is the one that decides the speed and the frequency of the turning of the axle and wheels in relation to the turning of the drive shaft. This is often referred to ring and pinion ratio.

Differentials are used on all modern cars and trucks , including AWD and 4WD vehicles and are typically composed of a gear mechanism in which a ring gear receives input power, which is transferred to two side gears by means of usually two opposing central pinion gears on a common shaft. The pinion gears are mounted to a cage which is affixed to the ring gear. When the ring gear and cage rotate, the pinion gears drive the side gears; the pinion gears are free to rotate about their own axis when either of the side gears meets resistance.

Most differentials nowadays come with a series of clutches and locks that allow each wheel to spin at different speeds. This includes Open Differentials, Locked Differentials, Limited Slip Differentials and Automatic Locking Differentials. In clutches, there is obviously some amount of energy that is wasted due to the slipping of the clutch plates. But this is necessary to one, engage the gears without damaging them; and two, allow the wheels to spin at different speeds. If the wheels were not allowed to spin at different speeds, the handling of the car would be drastically affected and the inside wheel would experience high temperatures and lots of wear, leading to a significantly shorter tyre life. Not to mention decreased efficiency and wastage of power.

Noises, vibrations and other irregular driving characteristics can often help diagnose a differential or driveline problem. Here are a few typical symptoms and their possible cause:

Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.

A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.

Rumbling or whirring at speeds over about 40 kph can be caused by worn carrier bearings. The noise may change while turning.

Regular clunking every few feet may indicate broken ring or pinion gears.

Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient lubrication, or worn clutches.

Rumble while turning may indicate bad wheel bearings.

A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.

Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts

Belconnen Transmission & Driveline Services are experts in differential problem diagnosis, repairs and replacements so no matter what the problem is we are able to diagnose faults easily and repair them cost effectively.

Use our contact form and we will call you back to book your appointment or call us today on 02 6253 1188 to discuss your power steering system needs. Alternatively just call in to our workshop at Unit 7, Carco Centre, Nettlefold St, Belconnen.


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