Hey guys. I've had numerous suggestions from many experts on what speedo drive I needed to replace the S13 electronic speedo sender unit in the gearbox.

I was told L-series Bluebird. This is not the case.

There are 2 kinds of gears profile, several colours (sizes) and 2 (possibly 3) diameters of the sender unit.

First kind of gear is very common and it's gear profile is fatter at the tip of the gear tooth, than it is at the base of the gear tooth. NO GOOD FOR S13.

The second type of gear profile is more a zigzag looking profile with almost triangular teeth, that's what you are looking for.

Commodore ones have the right gear, but are a larger diameter housing. NO GOOD. All have the black gear.

Now to extend upon the facts:
There are different gear colours, denoting the different number of teeth. The S13 5 speed comes with a Red gear.


Black (small dia) good for >4.1:1
Nylon
Red
Purple (large dia) good for <3.3:1

S13 replacements:
240K Automatic has a 17 tooth black gear
280C Automatic has a 24(?) tooth red gear

If you are running larger wheels and a mid 3.5 diff like me, then the larger "purple" gear is required. I'm yet to find one of those.

But for most people, looking under a 280C Automatic will yield the results you are looking for, if you are running 15inch wheels and ~3.9 diff. Assuming that you are using the 1200 speedo.

To install the gear, you either need to be very fast (like I was) or you'll need to remove the oil from the gearbox before starting. A mess will ensue if you choose not to heed my warning.

Before installing the geardrive, you need to cut/hand-file a step into the opposite side of the speedo drive housing (180deg). You will use the 6mm bolt and retaining clip, as used on the 280C. To understand what to file away, compare the S13 electric drive with the replacement mechanical drive, you'll see what I mean.

The Bluebird S3 (CA20) speedo cable is a good replacement for the 1200 with a CA18DET/SR20DET, as it's about 300mm longer.

Cheers.
Chris

I used a 120Y speedo cable on my CA conversion without any dramas.
Matty