Before my speedometer would tell me I was going 120 whenever I would be doing 40ish, and If I was going 25ish it would say 100. So I decided to get a new speedometer cable, I installed it and now it says im going 30 when i'm going 15ish. What is the problem I want to get my car on the road as soon as possible. Thank You!!

 

Where in NC are you located? Im in charlotte, if you're local I have a spare cluster would could try swapping the speedo unit out for.

Does the odometer tick along properly for the known speed?(1 mile every 2 minutes at 30mph, 1 mile a minute at 60)

 

Thank you for the offer but I'm in Wilmington and I don't really have time for a road until the winter haha. Also I'm not really sure about the odometer because a water hose busted and I haven't had time to fix it and check

 

I've got speedometer problems too, mine says I'm going 40mph when I'm going 60+ MPH

I've replaced the removable speed gear in the transmission (mine had one broken tooth) and the cable and still nothing changed.

I did try swapping gauges before installing both the cable and gear, it changed nothing but I'm going to try it again.

I'm also going to check the gear and make sure I didn't somehow damage it during installation.

If nothing fixes the problem I've got to assume the problem is the gear in the transmission (yet the transmission shifts fine).

The transmission was taken apart and put back together at some point because you can see orange sealer on the mating points of the transmission

If all fails ill be using a gps to see my speed until I can get the problem fixed, which may require me buying another transmission or getting mine rebuilt.

Rotary > Pistons

 

Could you please tell me where you got that speed gear and how to install it I'm thinking that is the problem with mine

 

If you look at the trans where the speedo cable screws in, you'll see the unit the cable screws to is held on the trans with one 6mm bolt. Undo the bolt and the speedo drive pulls right out with the driven gear.
This helical gear is made of a composite material and if there is a problem, it's far more likely to be the plastic driven gear instead of the steel drive gearing in the trans itself.

In the unlikely event that the gear is bad, Mazda probably sells the replacement as a unit, I doubt the gear is available separately.
All FCs use the same part, you might find one in a junkyard.

 

are you talking about this? I've taken it out before and it was. 10mm bolt holding it on or are you talking about something else.

I replaced it with one from the junkyard and still didn't fix the problem , I am gonba check and make sure I didn't damage it during install

the pic is the original I replaced, it had one broken tooth as you can see in the pic



Rotary > Pistons

 

6mm bolts have 10mm heads, heathen.
And yes, that's the part.

 

Yeah I don't know what the deal is, I'm gonna try using another set of gauges and going to check the gear I installed and make sure its fine.

Like you said I the gear inside the tranny being broken is unlikely but if I've fixed every other possibility its all it could be, how it got broken I have no clue.

Rotary > Pistons

 

When you replace the speedometer drive gear make sure you get the right one. There are different gears for the m type transmissions. Easiest

Details can be found at this link:Solomiata : Drivetrain : Interchange
Here's another from the first gen section that might help:
https://www.rx7club.com/1st-generati...r-tech-887141/

 

I got mine from an 88 na the gear color was the same so they should be the same.

Rotary > Pistons

 

Does anyone know of any websites where I can get a speedo gear? My local junkyards have no rx7's

 

I just checked the speedo gear and it's fine. So i have a speedo head in the process of being shipped as i type this as well as new shifter bushings

 

by speed head do you mean where the cable attaches to on the back on the gauges? I didn't know if that was removable

Rotary > Pistons

 

I kind of just assumed it was since they sold them separately. Oh well. If not i'll return it and get a new instrument cluster

 

how much was it? I might go this route in some way , either with one from a NA by taking it off or buying a new one like u did

Rotary > Pistons

 

It was like $50 off ebay

 

Alright turns out when you order from an ebay listing that says speedometer head only it is the whole instrument cluster. I just recieved it and installed it and now problem is solved. Now i can put tags on it and drive. So excited about my first car. Can't wait to fi other stuff on it

 

Fix not fi