Differential is not necessary for the front axle

[monty37]

why is it that the differential is not necessary for the front axle and is only in
the rear axle?

 

[FredGarvin]

Who says front wheel drive cars don't have differentials?

http://en.wikipedia.org/wiki/Front-engine,_front-wheel_drive_layout
http://auto.howstuffworks.com/differential1.htm

 

[monty37]

sorry if iam wrong,we were dismantling front and rear axles
our lab instructor told us that differential is present only in rear axle..as that's where
power is got directly,whereas front axles don't require that

 

[FredGarvin]

Perhaps your instructor meant that it wasn't a separate component like one would find on a rear wheel car? Technically I think that is the transaxle in a front wheel drive car. It's tough to say. I can't imagine driving a car these days without some form of differential.

 

[xxChrisxx]

OP

It seems your instructor is talking exclusively about rear wheel drive cars. Front wheel drive cars have a diff integrated into the the transaxle.

Only driven wheels acutally need a diff.

Non driven wheels don't need one because they are free to rotate at their own speed and arent driven.

Non driven front wheels can sometimes have a diff for torque transfer, but this is only typically on racing cars to improve traction and stability, during braking and cornering. The only notable one i can remember of is the BAR006 F1 car.

Also on many rear wheel drive cars you don't have a front axle, you'll have 2 stub axles.

Also do you know what the function of the diff is, and how it works?
Also do you know the difference between a driven and non driven wheel.

 

[FredGarvin]

He's talking about rear wheel drive cars. Front wheel drive cars have a diff in the transaxle.

Only driven wheels acutally need a diff.

Non driven wheels don't need one because they are free to rotate at their own speed and arent driven.

Well, yeah. I know this. I was simply stating that perhaps the instructor may have meant that only rear wheel drive cars have a differential as a separate piece of the transmission. The fact that a front wheel drive car has a transaxle does not mean that it doesn't have a diff.

 

[xxChrisxx]

I was acutally talking to the OP throughout the entire post but building on what you said (my poor writing skills ftw :P), I kind if guessed you knew all of the above. :)

Edited previous post for clarity.

 

[monty37]

the differential still bothers me.why is it that for non driven front wheels also differential is required,in what way does it enhance torque transfer?knowing the basic function and necessity of the differential,it
is only for allowing different speeds while turning right

 

[Ranger Mike]

in today's modern automobiles the transmission and differential are housed in a light weight compact alloy housing. this design is used for manual and automatic transmissions. The Trans is a series of gears that may be switched up or down as the terrain or load requires to keep the engine in a useable RPM range.
The Differential ( and ALL cars have these) is required to turn one drive wheel faster that the other when going around a corner. There is one draw back to this design in that the differential exactly splits the torque equally to both wheels. if one wheel is on ice and the other is not..the car will not move. This is why limited slip differentials came to be in that a series of clutches feed torque to both wheels when going straight yet the clutches permit over speed for the outside wheel when rounding a turn. In the old days we used to weld the spider gears in the diff and permanently lock the diff..all out racing only.. We then used stagger (put different size tires) on the wheels to compensate for the turning effect. if this was not done the car would spin out when rounding the corner.
Think of the Styrofoam coffee cup that is tapered, placed on its side on a table. when it is rolled it "rounds the corner"

one more thing..the diff does not enhance torque. it applies it to the drive wheel. the transmission multiplies torque thru various gears

 

[Mech_Engineer]

the differential still bothers me.why is it that for non driven front wheels also differential is required,in what way does it enhance torque transfer?knowing the basic function and necessity of the differential,it
is only for allowing different speeds while turning right

A differential's purpose if for applying power to wheels, and allows for each wheel to be spinning at a different speed (as is the case when turning).

If the wheels are unpowered, they don't have a differential (or any kind of axle) attached to them. I think if you're still having trouble with this, you aren't quite understanding the function of a differential...

 

[xxChrisxx]

I'm having troube understanding what his problem is exactly.

It sounds as though he thinks the undriven front wheels are connected, and a diff is needed to let them spin separately.

 

[Mech_Engineer]

It seems to me that things would be a lot clearer if he actually looked at what a differential is, it applies power through a driveshaft (or gear) to two perpandicular axle shafts. It should be obvious that it is meanigless to have a differential on a set of undriven wheels...

 

[monty37]

well iam clear now ,seeing the differential did help.

 

[Lsos]

I'm pretty sure differentials themselves also have a certain gear ratio, thus further increasing torque to the wheels.

 

[Ranger Mike]

note attached illustration. typical rear wheel drive differentials had ring and pinion gear that was the final drive ration. these were as low as 2.73 to 1 for automatic cars and went as high as 4.89 to 1 for performance cars although you can get oem or aftermarket gear up to 7.14 to 1 or custom made sets...the Dure grip pic shows clutches and limited slip design.
Front wheel drive cars have similar arrangement with final drive ratios of various sizes too.
hope this helps