Orange Cable SR20 S13 Transmission

[Ottawa510]

I am swapping the SR20 transmission into my Datsun, and I was wondering what the big orange wire (hollow, like a vacuum tube) is, and whether I need to hook it up. I looked everywhere and couldn't find out what it is.
Do I need to hook it up to anything? My feeling is not but I wouldn't want my shifting jeopardized by my ignorance. Thanks.

[torqued]

Breather tube

[Ottawa510]

Thanks. Also wondering about the transmission sub-harness - does it need to be connected to anything? I have the wiring harness from wiring specialties and it doesn't have a connector for the tranny sub-harness.

[JordanTr]

Depends what sort of functionality you're interested in. There's a neutral safety switch, reverse switch and speed sensor that are all on the tranny. I'm using a mechanical speedo and no neutral safety so the only sensor I've hooked up is the reverse sensor.

[akara]

Depends what sort of functionality you're interested in. There's a neutral safety switch, reverse switch and speed sensor that are all on the tranny. I'm using a mechanical speedo and no neutral safety so the only sensor I've hooked up is the reverse sensor.

The sr will work mostly fine this way, but from tuning my ECU I know that the SR20DET ECU actually has specific maps it uses when the neutral switch is engaged. It also uses the speed sensor on the ECU to hold the idle speed up a little before you have completely stopped.