i jacked up the rear of a rear wheel drive car and turned one wheel clock wise and whn i turned the other wheel also turned but anti clock wise,,,why is this happening ?i want to knw what is happening inside the diffrential.
It has to do with the limited slip action in the differential - ever notice when you lose traction ( in mud, loose gravel) only one wheel spins- the traction is supposed to go to the one that has the traction ( though it dosnt seem to work that way and you get stuck anyway). If it were a positrac - both wheels would spin the same direction- since theyre locked together.
The differential provides this action. It is a gear system which allows the outside wheel to turn faster and further on corners. As you corner, the drive comes entirely from the inside wheel , but if the outer one could not run faster (because it has further to travel) you would find controlling the car very difficult and wear out tyre's very quickly. The differential allows this to happen whilst always maintaining drive to one of the wheels. Limited slip differentials, mentioned in an earlier answer, are used on high performance cars intended for racing or rallying where it is preferable to have some drive on both (or all 4) wheels. Do not concern yourself with this. On rear wheel drive vehicles you can see the differential housing in the centre of the back axle, with front wheel drive it is usually incorporated into the final drive within the gearbox, but both work to achieve the same result.
The wheels all need to turn at different speeds as you round curves, and corners. The differential allows this. A differential consists of a ring gear, (aligned with the axial length of the vehicle,) and contains a minimum three spider gears that the axle gears drive off of. As the car enters a turn, the spider gears on the ring gear allow one wheel to turn faster than the other. A Lego drive set can illustrate it best for you. Due to torque and friction, a standard, (the one you referred to,) slip differential typically applies power to the tire that has the least traction; it's the most inexpensive to produce due to mechanical simplicity, resultantly being the most common on the roads. Positrac, common on older muscle cars, basically locks the rear end, (another word for differential or final drive,) under heavy acceleration. Locking differentials mechanically lock both axles together when centrifical force from a single wheel spinning mechanically engages the other axle. In a turn, front tires, left and right, rear tires, left and right, are all turning at the same speed, so all-wheel-drives feature a center differential to allow the wheels to maintain maximum grip on the road in a turn. And many 4x4 enthusiasts, invest in aftermarket, selectable, differential locks to ensure that if one wheel slips, (or is just hanging in the air,) the other three wheels have power to them. If you've friends with RC cars, they can show you the inside of a differential much more easily than you can disassemble the rear end of your car. Other sources would be Chiltons manuals, Haynes Manuals, and you'll likely never believe the brilliance of century old engineering until you actually witness it in practice. JT
