The Difference Between AWD and 4WD and Differential Repairs
The differential is responsible for allowing your tires to move at different speeds when necessary, such as every time you make a turn. But what’s the difference between AWD and 4WD differentials and differential repair?
4WD differentials transfer the same amount of torque to all four wheels to make them move at the same time. Conversely, AWD supplies differing amounts of torque to each tire. 4WD normally has 2 differentials, while AWD can have up to three. The main difference in differential repair comes down to how easily each differential component is to access and make the the repair.
The Difference Between AWD and 4WD Differentials
Between your front-wheel differential and your rear-wheel differential there is a transfer case and drive shafts, where the transmission of your 4WD car is connected to the transfer case. Inside the case, there are two drive shafts, one for the front wheels and one for the back wheels, where each spins the axles of their respective set of wheels.
When the driver engages 4WD in a part-time 4WD, the transfer case will lock the two drive shafts together in order to allow each axle to receive half of the torque the engine is generating. The purpose of this system is to increase traction, but it is only recommended for use on rough or off-road terrain and not smooth or even slippery terrain because the amount of torque the engine sends to all of its tires can only keep the tire with the least traction from slipping.
AWD cars will normally come with three differentials. There’s one for the front wheels that allows them a slip, but not necessarily a differential slip. Then there’s one for the back wheels that does the same, and then the center differential that mediates the two. Slip refers to the feature where a wheel will not receive torque if if is not gaining traction. Not all AWD cars have this set-up. Some get rid of the central differential and replace it with a torque coupling. This system is preferred for paved roads and slipperier surfaces because it’s flexible with how much power each wheel gets.
Many drivers overlook that differentials require preventative maintenance. Aside from regular oil and fluid changes, differentials also require attention from time to time. The fluid inside should be changed in accordance to manufacturer specifications.
If you experience leaking, differential repair involves replacing the sealant gasket or the differential breather. The breather is a vent that helps distribute heat generated by the differential.
If you have to replace the differential gears and/or pinion your mechanic will essentially have to rebuild or replace the component that is failing. In most cases it is better to replace the part with a new or refurbished part. The good news is that you can send the damaged part back to the parts supplier and get a credit (core).
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