What are they and what does locking a diff do. what do they do in a whole

A diff alows the outside wheel, of a vehicle that is turning, to turn backwards. Thusly the outside wheel turns a lesser distance. Giving you a smaller turning radius.

With that said......locking the diff doesn't allow the outside wheel to turn backwards. A lot off offroad/rock climbing people lock there diff for when one wheel comes off the ground, not power is giving to that wheel, and all the power of the motor is givin to the wheel that is making contact. Giving you more umph to get over the obsticle.

Hope this helps,
Haydn

so if im doing carpet racing would it be helpful to lock the rear ？

No!!! Locking the rear diff would hurt you, because your turning radius would be greater....and you wouldn't be able to turn as good. Although having you front diff alittle tighter than your rear would give you better pull out of the corners. What car are you running?

right now TT-01 but im thinking of going to a Pro 4

Pro-4 is a great car! but yes make sure your front diff is tight, but still can turn, and that should drive alittle better off the corners.......

Daddy, I asked a similar question tonight and got some good info, thought it would be helpful for you...
[link]http://www.rcuniverse.com/forum/m_3942171/tm.htm[/link]

Haydn. You need a correction here. The outside wheel turns a greater distance than the inside wheel, and it doesn't turn backwards. It is still going the same direction as the inside wheel. A locking differential prevents this and both wheels turn at the same speed. This is perfect for drag racing. But even in road or oval racing it can work too as it will help induce oversteer. And if one wheel comes off the ground that side will "unload" as all the power will go to that wheel and not the wheel with the traction. That's where a "limited slip" differential will help. Or if it is locked that won't matter. But if it is a design called a "Torsen Differential" then the power will got to the side with the traction because it uses worm gears which can only rotate on direction and lock in the other so it won't unload.

Yes you are right. Thanks for the correction.....I thought that in my head, but for some reason it didn't come out right. Thanks,


Nathan