[AnubisXII]

Hello, lady and gentlemen of the forum. I was wondering if one of yall could tell me how to go about finding out which part of my speed notification system needs to be replaced.
What's Happening:
My speedometer usually sits on zero. Whether I'm going faster than that or not. Every once in a while, I could look down and, "Wow! It's working!". But then, it's not.
So, in a nutshell... My speedometer stays at zero most of the time. But once every blue moon or so, it works.
I need to see what I can do to get it working again, but I don't know how to go about troubleshooting anything besides the cable connections. Someone told me to unhook the cable from the back of the speedometer and see if it spins while I'm moving. That's all fine and dandy if I had someone willing to sit in the engine compartment while I'm rolling forward, I mean... That would be the only way to do that, right? I have to pull my dash to disconnect the cable, but put it back in place to drive. So I'd have to pull the cable back through the firewall in order to see if the end spins. And whether it does or not, how do I find out if theres something else wrong without replacing everything part by part until finding the part I've should have replaced first? I'd like to do it that way, but my finances dictate that I replace the right part the first time.
Thank you.

 

[6T6Coupe]

Option 1 - block up the rear wheels. If you can hold onto the inside cable (behind dash) while the rear wheels are moving, the cable is bad. This is the way i did mine - rear wheels up on stands. Safer.

Option 2 - Im not sure about the 1971's but you can drive a '66 with the dash piece laying on the steering column (protected with a towel or something)...same deal the cable should keep spinning even if you try to hold it still. But then ya got to drive & deal with holding the cable.

My problem was kinda like yours, (it would work once yearly.) It was a $7 part that goes into the side of tranny. The speedometer gear. There are many different amount of teeth available and also need to see if its right side or left side drive. Mine was a 16 tooth gear. they are just plastic & wear out. I R/R mine with the same 16 tooth that was in there (4-5 teeth were worn down)

Maybe someone with a 1971 or close to that will help out here. most Mustang supplier places stock them. Good luck. :yup:

 

[72 fastback]

The dash pad comes out real easy in them years. Once removed you can access the back of speedometer. You could jack up the car remove cable and hook a drill up to it and see if the speedo moves.

 

[AnubisXII]

Thanks! I'll let yall know what I find (like, I'm sure you're losing sleep over this one).