3 channel or 4 channel

[slowmaro305]

I hear talk of 3 channel and 4 channel rear ends when looking for stock used ones.

What is the difference between the 2 and how can i tell by looking at them? Any pictures for reference would be great.

Thanks.

[Hot Black Trans-Am]

3 channel is without traction control and 4 channel is with traction control.

[oldmanZ28]

3 channel has the reluctor wheel sensor at top of the rear end,4 channel has a sensor at the reluctor wheel on the end of each axle(sensor located in backing plate/dust shield)

[slowmaro305]

thanks