Okay, if you are looking to build a K'nex differential. Then I probably do not need to tell you what it does.

If you don't know what a differential is, watch this video.

Step 1: Gathering Materials

This is one of the smallest K'nex differentials. Also This doesn't use a lot of parts.

Following is a list of the required Parts

6x Blue 7 pins connector

6x Purple 4 pins connector

2x Yellow Half round connector

8x red quarter round connector

7x White round connector

2x orange 2 pins straight connector

2x Red rod (5 1/8 in)

10x yellow rod (3 7/16 in)

7x blue rod (2 1/4 in)

5x white rod (1 5/16 in)

20x Green rod (3/4 in)

8x light blue spacer

6x gray spacer

1x yellow gear wheel big

2x yellow gear wheel medium

2x grey gear wheel small

Total Part count: 94

Step 2: Building the Gear Room

Okay this is an easy step. I suggest First making the blue rod with the 2 yellow gears. Then building the housing around it.

Now, time to make the two axles.

The last step is to make the stand so you can present it (for instance).

if you correctly followed my steps you should end up with something that looks like this