Differentials and Transfer Cases (4WD)

Servicing and Tips for Differentials

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The differential is an essential part of your car. Without it, turning corners in your vehicle would be difficult.  The differential gives the wheels of your car or truck the capability to turn at different rates. Because the inside wheel travels a shorter distance when a car turns, the car needs a differential.

All vehicles have differentials of some kind. In front wheel drive vehicles the differential is in the front and called a transaxle. In rear-wheel drive vehicles, the differential is in the back. Four wheel drive vehicles run power through the transmission into a transfercase and then too front and back differentials.

The differential contains fluid that lubricates and cools the gears. As with any other lubricant, differential fluid breaks down over time.  Along with the engine, the differential is very particular about its oil and condition.

You should consider getting your front or rear differential fluid checked more frequently if:

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Servicing is limited to oil changes at the recommended intervals.  The harder you drive, the quicker your differential fluid breaks down.  You should consider getting your front or rear differential fluid checked more frequently if:
 

• You frequently tow a boat, caravan or trailer
• Your vehicle’s rear axle is partly submerged when you launch a boat from a boat ramp    
• You drive in severe conditions e.g. road covered in snow
• You are an off-road enthusiast and cover rough or wet terrain

There are two common problems that can occur in your differential, and these aren’t necessarily fixed by a service:

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• Noise – usually when you hear any kind of noise in your car it’s due to the result of either wear or component failure.  The grinding of the gears will produce a growling sound and can become louder when taking turns. If this is put off it can result in a major (and expensive) car repair.
• Leak – when there is a leak it means some parts somewhere are not being properly lubricated. An unchecked leak can lead to the growling noise and can escalate from there. Always  have any oil leaks investigated by a qualified professional.

Servicing and Tips for Transfer Cases (4WD)

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The transfer case takes power from the transmission and splits it between output shafts that connect to the front and rear driveshafts. The transfer case is what makes all wheel drive work.
Transfer cases are either gear driven or chain driven. Most of the transfer cases made today are chain driven because these Transfer cases are quieter and lighter.

 
Servicing is limited to oil changes at the recommended intervals.
 

• The transfer case is always working, whether you use the four wheel drive on your vehicle or not. Your transfer case fluid level should be checked every time that you get an oil change.
• In the old days, transfer cases were filled with gear oil or automatic transmission fluid (ATF), but some modern transfer cases take specialty lubricants.
• It is important with permanent 4WD vehicles that all tyres are the same brand, size and wear level as a difference in circumference can increase wear in the unit or at minimum a knock or harshness on lock.
• Selectable 4WD’s generally are designed for use on soft or slippery surfaces only and not for general road use.