My speed sensor drive worm gear inside my trans has worn out and Ive looked everywhere to find a replacement. Seems like you cant get them anymore. Does anyone know where to find one?
Could I replace the worm gear and sensor with one from a miata or something so that they are a matched set?

 

That's a pretty uncommon problem. I would just track down a good used one off an old transmission or something.

The drive on the sensor and the drive on the transmission should be a matched set I believe. They need to be the right gear set so they match the gearing in the car and the rear end. If you got one from another car it may be set for that car's gearing which would throw the speedo off.

It may be available new from Mazda, you would need to dig into the parts catalog and find the part number. Or call Ray Crowe, he can probably find it for you very quickly and give you a good answer as to price and availability.

Dale

 

Ya, I looked up the oem part in the manuals. Mazda doesnt have it anymore and MazdaTrix says they cant get one.
Who is Ray Crowe?
And I am ok with it changing the speed output, Im running a stand alone so i can adjust it from there.
Also I hate to admit but its my fault it wore out. I am running a FD trans in my FC and had the FC cable driven sensor plugged in to plug the whole temporarily and the gears ate each other (Cries in Brap)

 

There would be lots of people who have blown their boxes, all you need is to grab the extension housing off one of them.

 

I was surprised to find that the plastic gear inside the gearbox is actually the same for the different ratios, it's only the sensor that changes, making it an easy one to swap out when changing ratios. This was checking between 4.1 and 4.3 ratio calibrated sensors. I cant say if it is the same for 3.9 auto.

 

Interesting! Good to know!

Back to OP, the FC uses a cable drive speedo and I don't know if it could easily (or at all) be made to work with the FD trans. If you want to use the stock speedometer, you may want to look into how some of the V8 guys have done it.

If you aren't using the stock speedo you can use one of the speedos that use GPS signals to display speed then you wouldn't have to fool with the gears at all.

Dale

 

Ya, That gear is also inside of some mazda MPV vans and the 929. But im giving in an getting a GPS that outputs a Square wave so my MaxxEcu will have a signal. Im not using the factory dash, Im using a tablet dash.
I'm using the FD trans cause its got a longer input shaft I needed for my engine swap. All I had to do was swap the FC rear housing on it and it all matches up.

 

if you really wanted that gear, R502-17-341A, it looks to be available in Japan still, Amayama can get it

 

Holy smokes! I'll order one up and hopefully it works. Thanks a bunch Mah Dude.