SOLVED!!!Speedometer cable UPDATE and help

Speedometer just replaced and functions now...problem is, it's off by a good 20mph. It's always been off since I've owned it because of the staggered tires and such, but never by this much. I'll be going 40mph and it shows 60mph+. I know our cars are fast but come on...how do I fix this?

Problem resolved: Thanks to those who suggested to get a gear with more teeth. Went from the green one (17) teeth to a 21 teeth (red) and it is spot on!

That is what the original cable looked like on my car, I swapped it out to a 1 piece and it fits just fine. I'm guessing maybe it is a speed sensor on your cable for cruise control. My engine and trans where long gone when I bought the car so who knows what mine came with.

The three position connector based on the wiring diagrams is connected to your door jam switches and is for the under dash courtesy lights. If you post a better picture of the other connector I should be able to figure out what it is as well.


The connector in the last picture, is it black with 6 positions?

I think that is connector C-1003

Starting in the upper left and working left to right, top to bottom, the pins are:

1. 260 R-O

2. 269 LB-O

3. 261 O-BK

4. 348 LG-P

5. NC

6. Brown

They look to be part of the Heater/AC circuit and connect to the Mode Select switch on the center console, as well as the blower motor resistor and a few other bits like that

That is a speed sensor for the emissions. Mustangs never had cruise control. If I recall, it has to do with the EGR system. Does your engine have an EGR valve? I didn't think Mustangs had them until 1973. I could be wrong though. If you do not have such set up, you should be fine to hook up your speedo cable without the adapter.

-Travis

Thanks for the help...I'll probably just use the 1-piece option then.

Need some help with what I'm working on...

I have the new speedometer cable and after reading other forums, do I need to have the new speedometer with that adapter or is it fine to use the new ones that are just one piece? Here is what the original looks like...

And in the other photos, what are these wires behind the gauges? the last photo shows where they end up which is on the passenger side glove box.

Click to expand...

Doug is right had that in 73 parts car. it pluged into red box under dash with circuit board inside controlling ignition vaccume advance and retard not sure if I remember if it had a outside air temp sensor in the driver side door jam about where the interior light button was.

Doug and Red are correct

That is a 73 only part.

You can see the speed sensor being called out for the 73 here:

http://www.mustangbarn.com/images/vacs/73%203-14A.jpg

It's obviously not called out on the 71/72

My 73 has the speedo sensor attached to the cable. I would really wonder how or why it got put on to a 72 car. If it has the electronic amplifier that the electrical plug goes to then you have to wonder if your dash is from a 72 or 73?

I'll have to double check. I'm kinda wondering that myself....thanks for the info.

Help...speedometer off by bout 20 mph

what transmission, rear end gear ratio and tire size are you running?

With this info we can determine the proper speedometer drive gear. It is a 1 bolt one clip change out that takes about 5 minutes if you are slow and clumsy.

http://www.bgsoflex.com/speedo1.html use the cable rotation at 1000 rpms and this will tell you what gear you need for calibration

http://www.transmissioncenter.net/speedometer_calibration_______va.htm gears and cables are here

http://www.cjponyparts.com/1964-1973-mustang-speedometer-gears/c/10190200/?gclid=CMaOxIXprL0CFUYV7AodcVUAbQ and here

And Don of OMS will have them as well and he is good to deal with.

^ +1 to that

Did you get it worked out?

I'm gonna work on it this weekend. I'll will keep you posted. Thanks.

Tom,

Do know if the rear gears are original?

As a general rule of thumb, isn't about 5- 7 mph for every tooth in the cable gear?

So if you are showing 20 mph too slow, you need to reduce the amount of teeth.

Tom,

Do know if the rear gears are original?

Click to expand...

I'm really not sure. I'll find out when my mechanic friend comes over this weekend. I'm focused on getting those brakes fixed asap and then I will jump that.

As a general rule of thumb, isn't about 5- 7 mph for every tooth in the cable gear?

So if you are showing 20 mph too slow, you need to reduce the amount of teeth.

Click to expand...

It's not too slow, showing too fast. Spedometer shows 70+ when really I'm only going 50mph or so...must be the jet fuel I gave it....haha...joking

So, your speedo gear is turning too quickly. That tells you it doesn't have enough teeth. a reading of 70 when going 50 is 40% too high.

Count the teeth on yor speedo gear, multipy by 0.6 and that will give you the number of teeth you really want.