I am in the process of replacing the original trans (rebuilt 3 times that I know about) with one out of a 2nd gen turbo. I have all the necessary parts & the physical swap is pretty straightforward. My question is about the backup switch.

The backup switch on the original trans had 4 wires coming out of it. Two were for the backup lights & the other two were for the "5th gear switch" (according to the factory shop manual). The 5th gear switch is also referred to as the "over the top" switch in some of the wiring diagrams. It appears that one of these wires goes to the ECU & the ECU's pin voltage varies depending on which gear the trans is in.

The backup switch on my T2 trans is broken off right at the metal housing so I can not tell how many wires were coming out of it. Mazda, of course, has discontinued this part so I will have to search junk yards for one. I can't tell from the wiring diagrams in the manual whether or not it connects the same way as the old trans (4 wires or just 2 for the backup lights).

Now for the questions:
1. Does anyone know what the downside is to not having the 5th gear switch connected/functioning?
2. Can anyone with a T2 tell me how many wires are coming out of the backup switch?
3. If there are only 2 wires coming out of it for the backup lights, where do I connect the other 2 harness wires for the 5th gear switch?

Thanks,
Don

 

I just looked in my 1988 workshop manual & the back up lamp/ 5th switch have the same part number (N/A & TII) this tells me you can swap them with each other.
On the TII it's called "back up lamp / 5th switch" and the N/A it's called "5th / reverse gear."
So if it's not connected "5th switch or reverse gear switch" you will not have reverse lights I hope this helps good luck!

P.S the TII & N/A have four wires.

 

Thanks for checking this out. My original plan was to just swap the switches until I compared them.

The backup switch in the old trans has a smaller diameter threaded section than the turbo version. The "plunger" portion that goes into the trans is also different. The turbo version is well over an inch long while the other one is less than a half inch.

Now that I know the turbo version does have 4 wires I'll probably try soldering some onto the broken switch. No guarantee that I can get them to stay on or that the switch still works but it is worth a shot.