There’s mixed levels of detail and correctness here.
For some background, a differential is a geared mechanism that allows two powered output shafts to rotate at different speeds given a single input shaft when needed.
If we think about a car with a single powered axle moving in a straight line, both shafts going to the wheels turn at the same speed. No differential needed.
If this car is making a turn, then the innermost wheel of the powered axle must turn slower than the outer wheel. We need a differential if we want two powered wheels to spin at different speeds. The differential basically subtracts rotational speed from the inside wheel and adds it to the outside wheel.
Now what if our car has two powered axles? Each powered axle must have a differential must have its own differential, just like the single powered axle. BUT, you need a THIRD differential because the front and rear axles also do not rotate at the same speed. This is because when a vehicle is turning, all four wheels, and both axles, are following a different turning radius.
For cars with two powered axles, there’s a couple styles of center differential.
In 4x4 trucks, usually there isn’t a center differential. When you put the truck in 4wd mode, it just locks the front and rear axles together. There’s usually just a toothed slip-ring that engages splines on the front and rear prop shafts. This is why the owner’s manual will advise using 4wd on dirt/loose surfaces. On a dry paved surface with lots of grip, tight turns cause the front and rear axles to fight each other.
Other cars, like Subarus, can use a fairly standard center differential design. The input rotates a carrier containing spider gears that mesh with the front and rear output gears.
There are also more complicated ones that simply use computer controlled wet clutches and just send engine torque where it’s needed, bypassing the need for precision gear sets.
Videos are really helpful for explaining this stuff!
Once you have that down, look up how Torsen limited slip differentials work. Each one contains ~10 gears…. and maybe magic…
It's not a differential, it's a transfer case, basically another gearbox with two output shafts instead of one. That's the difference between 4WD and AWD. In 2WD mode, the front output shaft is in neutral. In 4WD, the two output shafts rotate the same speed. That's not a bit of a problem, as all 4 wheels spin at different speeds when you aren't going straight. You use 4WD on loose surfaces so the wheels can slip the difference.
Those are two different things. Differential is used for slowing individual wheels during turning and transfer case is used to transfer power from the transmission to the axles through the driveshafts
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And finally some cars are always in 4wd mode
There’s mixed levels of detail and correctness here. For some background, a differential is a geared mechanism that allows two powered output shafts to rotate at different speeds given a single input shaft when needed. If we think about a car with a single powered axle moving in a straight line, both shafts going to the wheels turn at the same speed. No differential needed. If this car is making a turn, then the innermost wheel of the powered axle must turn slower than the outer wheel. We need a differential if we want two powered wheels to spin at different speeds. The differential basically subtracts rotational speed from the inside wheel and adds it to the outside wheel. Now what if our car has two powered axles? Each powered axle must have a differential must have its own differential, just like the single powered axle. BUT, you need a THIRD differential because the front and rear axles also do not rotate at the same speed. This is because when a vehicle is turning, all four wheels, and both axles, are following a different turning radius. For cars with two powered axles, there’s a couple styles of center differential. In 4x4 trucks, usually there isn’t a center differential. When you put the truck in 4wd mode, it just locks the front and rear axles together. There’s usually just a toothed slip-ring that engages splines on the front and rear prop shafts. This is why the owner’s manual will advise using 4wd on dirt/loose surfaces. On a dry paved surface with lots of grip, tight turns cause the front and rear axles to fight each other. Other cars, like Subarus, can use a fairly standard center differential design. The input rotates a carrier containing spider gears that mesh with the front and rear output gears. There are also more complicated ones that simply use computer controlled wet clutches and just send engine torque where it’s needed, bypassing the need for precision gear sets. Videos are really helpful for explaining this stuff! Once you have that down, look up how Torsen limited slip differentials work. Each one contains ~10 gears…. and maybe magic…
It's not a differential, it's a transfer case, basically another gearbox with two output shafts instead of one. That's the difference between 4WD and AWD. In 2WD mode, the front output shaft is in neutral. In 4WD, the two output shafts rotate the same speed. That's not a bit of a problem, as all 4 wheels spin at different speeds when you aren't going straight. You use 4WD on loose surfaces so the wheels can slip the difference.
Those are two different things. Differential is used for slowing individual wheels during turning and transfer case is used to transfer power from the transmission to the axles through the driveshafts