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what is a differential

A differential is the driving-axle gear assembly located in the center housing between the driving wheels on rear-wheel drive vehicles, or as part of the transaxle on front-wheel drive vehicles or between front and rear differentials on all-wheel drive vehicles. The differential transmits power to the wheels while allowing each wheel to rotate at different speeds, such as when turning a corner.

Why is it needed to lock the differential in certain conditions? If a wheel loses traction (the wheel is on ice, snow, mud, or raised in the air), an open differential will send all available engine power to that wheel. The wheel will spin, but the car will not move. So even if a vehicle has all-wheel drive, but neither of the three differentials can be locked, it is enough for just one wheel to lose traction (to spin) and the car will not be able to move.

So, to get the car moving, it is necessary to lock a differential. Locked (or limited slip) differentials make (or try to make) the wheels to spin at the same speed, syncronously. This transfers torque from the wheels that spin to the wheels that have traction. Ideally, a vehicle should be able to fully lock all three differentials (center, rear, and front) - in this case the vehicle would be able to move as long as just one wheel has traction.

Figure: Free differential (90KB)

Figure: Limited slip differential (83KB)

Read more: How a differential works

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There are 13 comments
February 03, 2022 - 18:36

Ok I just brought a 2012 Hyundia Santa fe se. Sometimes when im driving it feels like thebleepedend jerks when I break and then accelerate. I was thinking it could be the read diff but im not sure. Can someone please help. Thank you

September 26, 2016 - 21:00

Can I drive my 2005REAL TIME 4wheel drive if the ujoint went out?2wheel drive? And how do I comlete this task?Help is greatly appreciated

June 19, 2015 - 12:47

I'm planning a purchase of a 4x4 that does not have a Diff. I'm just wondering about the necessity of the diff when you have 4x4. what are the draw backs of not having one?

February 04, 2015 - 16:00

Marxxon-Car Differential Manufacturer


March 21, 2014 - 11:59

I have a kia sorento '08 AWD, and lately i heard strange sounds that i think comes from the front axle... i am planning to convert the AWD to RWD since i don't need 4x4, so is it alright if we'll just take out the front axles?


December 07, 2013 - 09:28

Hi i have just got a rav4 1995 and its my first all wheel drive, i have engaged the diff lock to see what it did and then disengaged it but now there is an alarm beeping all the time while the diff lock is off and only stops when i engage the diff lock again, i would love to know how to stop this please?

Reply to Jason
February 11, 2014 - 01:48

You need to reverse

April 06, 2013 - 04:05

I drive a 1992 80 series landcruiser wagon gxl all wheel drive. It broke down at the lights and there was a grinding noise from the front diff I think. The car drives in 4wd then a mechanic said to put back into high and press the centre diff lock button. The car drives through the back wheels. Now when I was showing a mate the car won't engage back into centre diff lock or even go into low 4wd. Any help??????

November 04, 2011 - 12:49

I need to understand this... I am driving a 2001 land cruiser. Which has a differential knob on the left of the steering... Driving through rubble and rocky area should I put this on and then drive in 4 wheel mode?

Reply to Viv
November 07, 2011 - 21:21

The US market Toyota Land Cruiser had a center differential, so there is no single axle drive mode. [rear]
I would lock the center differential before attempting crossing a wet/mud obstacle, or where a loss of forward progress could mean a lateral slide (or roll over)
If the rocks/rubble are loose enough, then there won't be appreciable drivetrain windup.

November 12, 2010 - 09:49


January 06, 2010 - 11:37

When I push a button to block a central deff. (Toyota LC-105), and trying to turn after the defferential clocked, I can hear strange noise like, would say a crackle from the front wheels. What can it be?
Thanks beforehand.

Reply to Igor
June 04, 2011 - 11:58

every thing. do not lock your center diff on anything but the sliperiest surfaces, consistent ice/snow mud sand.. Your center lock most likely is not a true lock maybe something like a clutch pack in a posi dif or a torsen settup this sound is prob the center diff giving in one way or another to allow some wheel speed differance front to back. Dont fret you didnt break it, you just put some extra wear on it.

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