Replaced broken odometer gears - still not working

1987stangman

Member
Jul 12, 2006
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I finished up my PI motor swap this past weekend and I figured what better of a time to fix my broken odometer than now. I removed the cluster and both gears were broken so both got replaced. Took the car for a spin and still no go. I guess there is a good possibility the little motor that moves everything could be broken but through my searches I have read some stuff that a bad speed sensor or VSS could be to blame. Anyone else run into this?
 
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I ran into this problem as well. After installing my odometer gear, the odometer would initially work, but after less than 1 mile, it would stop working. It turned out that I had a bad gear. One of the gears was missing a tooth, so it would stop working soon as it rolled around to the missing tooth. I contacted the company which I bought from and after some picture proof, they sent a replacement.

That is a bit of an odd situation, but worth a check. By now, you are good at taking it apart I'm sure.

You said you did a PI swap? Did you retain the same VSS sensor as the car had when you took it apart? The newer (PI) VSS sensors are different and not compatiable with the older ones as I recall.
 
I ran into this problem as well. After installing my odometer gear, the odometer would initially work, but after less than 1 mile, it would stop working. It turned out that I had a bad gear. One of the gears was missing a tooth, so it would stop working soon as it rolled around to the missing tooth. I contacted the company which I bought from and after some picture proof, they sent a replacement.

That is a bit of an odd situation, but worth a check. By now, you are good at taking it apart I'm sure.

You said you did a PI swap? Did you retain the same VSS sensor as the car had when you took it apart? The newer (PI) VSS sensors are different and not compatiable with the older ones as I recall.


Taking it apart is a no-brainer for sure. As far as the VSS, I have not researched it's exact location but I figured it was on the tranny (I have a 4r70w) in which I am using the stock 96' tranny the car originally came with. The only thing that changed was the engine. I reused all my old NPI stuff right down to the fuel injectors, timming cover and oil pan. The only thing that stayed was the PI cam covers and intake.

From the research I have done, the VSS/Speed sensor on these care operates the speedo and the odometer and everything works execpt for the odometer. I had plan to take it back apart this evening but got tied up helping a friend with his own engine swap in his F-150. The only thing I can think of is maybe I failed to find all the little fragments of gear teeth from the old broken gear.
 
yep, the VSS is attached to the transmission. I asked because I didn't know if you swapped the whole engine (and transmission) or heads.

The speedo gear set is pretty sensitive. As I recall, there was a tiny motor to operate the odometer seperately from the speedo and that's what the worm gear mounts to. Make sure you plugged the motor back in? Did you get the driven gear set firmly in place? It is a tight fit and pops in roughly. You can try rotating the gear train before putting that motor back in. It should be smooth. :shrug:
 
I did plug the motor back in, that I know for sure and there is only one way it will snap in. I will pull it tomorrow after work and see. I'm hoping all it is is that there is some debris causing it not to spin. I was acually shocked it didnt work after I installed it. I will post what I find. I def need to get it fixed.
 
Saw your post. Interested in outcome. I'm next.... Never took gauges out of car before, a little scared!
Thanks

Gauges are a piece of cake to take out on our cars. I have a little newer mustang but its really similar inside and would guess its close to mine there as well. Take the headlight knob off, 2 screws on the underside of the bezel/dashpad and then that front piece will pop out. Then it is 4 screws and pop the 2 wires off the back and it should come right out and allow you to work on the cluster outside the car. On the newer cars its recommended that you disconnect the battery but I don't think you would have to do that since its gear driven and not digital.
 
1987stangman:

Warning, warning: be careful when you remove the VSS from the tansmission and when you put it back in. It is held on by a single small bolt. Don't lose the bolt and don't overtighten it when replacing the VSS (and take care when putting it back in - don't force it).

OK, now let's get to the next part. You can check the VSS output with a multimeter. It puts out AC voltage (yes, it's true). Spin it with a drill (slow speed and see if you get any voltage. Next, plug the VSS into the harness and run the drill while watching the speedo-odo in the car with the key turned to the ON position (dash lights on but engine not running). If all is well, both should be working. If they don't move then you have to take the cluster out again. Make sure that the speedo needle is not dragging on the face of the cluster. Don't push on the needle and don't move it with your finger. You just want to make sure that there is daylight between the needle tip and the plastic face with the numbers on it. If it is touching, you can use a salad fork to move the needle us JUST A TINY BIT on the speedo motor shaft. This is a very delicate operation so take your time and don't make like the Incredible Hulk.

HTH,

Chris