Speedometer questions

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HTMLmopars

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I've been using this site to help with my 225 to 318 swap, but this is my first time actually posting, but y'all ate super helpful. I'll get to the point now.
My speedometer hasn't worked ever, well its had a couple minutes of time that the needle moved while driving but it wasn't accurate at all. I'm directly using my phone as a speedometer to get to school and work but I'm getting tired of using it, so I want to know if I should try to fix the factory speedo or buy and aftermarket one. The only reason why I'm hesitant to buy an aftermarket one is because I don't know how the digital ones get information from the car. Running a stock 904 if thats important.
Also I've already lubed the speedo cable with no results at all. Any information on this is helpful
 
I would pull the speedometer pinion gear out of the transmission and make sure the teeth on it are good before doing anything. If they are not clocked correctly for the tooth count it will either chew them up or not make contact with the drive gear in the transmission. While you are under there you may as well look for a tag on the rear end as to the gear ratio so if you need a new pinion for the trans you'll have a start point for the tooth count needed. If no tag you can spin a tire while counting number of turns on the driveshaft. It will get you close.
 
One problem can be that the speedo cable's ends are not set into the gear into the trans and into the speedo gauge; they can be tricky to re-engage at both ends. Pull the end of the cable at the trans, not the gear itself, at the trans and carefully re-engage the end into the gear. Also, look at the end and the hole in the gear to make sure they are not worn; they should be square. You can make sure the trans end is engaged by having it disconnected at the upper end and moving the car a bit to see it turns. Then to the same at the speedo end; turn the speedo input hole so it will be lined up with the core out of the cable; if not they will often not engage.

If the cable is engaged for sure, then the speedo's do go bad. I have always replaced them; but a few have carefully disassembled and repaired.

And electronic speedo uses a sensor at the trans or at the upper end of the cable. That turns the rotation into electronic pulses.
 
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