sflodkvist

Hi
I have an issiue I hope you can help me and my 64½ Mustang.
I have recently bought the car here in Sweden and the speedometer was one thing to fix as it did not work.
After some testes (including replacment of speedometer) did I find out that the speedomeeter show your speed, but only when you are driving with reverse gear.
I have a manual 4-speed transmission in the car.
I was recomended to replace the drive gear on the end of the speedometer cable as there are two types, one with the the teeths turning to left and one to the right. Regardless of which I use do I get the same result, driving forward -nothing is shown on the speedometer, going back, the speedometer starts to show your speed.

Please help a confused Mustang owner in Sweden

67t5ponycoupe

The speedo must be turning in the correct direction when in reverse and the incorrect direction when going forward. That means the speedo head, cable and driven gear are all going backwards when the car is moving forward. The only thing I can think that would do that would be the drive gear on the tailshaft of the transmission. The automatics and the 3 speed had the cable going in the tailshaft on the drivers side and the toploaders went into the passengers side. It sounds to me like the drive gear on the tailshaft needs to be changed to the correct one.

Gun Jam

+1

Do you have the only classic mustang in all of Sweden?

sflodkvist

Thanks for your quick reply 67t5ponycoupe
.
yes, my cable is attached to the right side (passanger side) of the tailshaft. From my understanding do I need to change drive gear in the tailshaft then to get the correct rotatiion on the speedometer cable?

Gun Jam, no, there are plenty of them in Sweden and I have contacted several people also members of the club but non of them have had this issiue.

KMatch

The differences in rotation of the gear on the cable are only to allow it to mesh with the right gear on the trans output and like was discovered, won't change the direction. I can't think of one instance of a backwards speedo so that makes me wonder what really is going on here. Any way you look at it, it's got to be the trans output shaft/gear, but it still doesn't make sense to me on the reverse rotation. Being on the opposite side I'd think it would still have the correct cut unless the drive gear is a slip on and someone screwed up and installed a wrong one.

67t5ponycoupe

The more I think about it the less sense it makes. Everything poonts to the drive gear but what would make it do that? The 3 speed and 4 speed transmissions use the same drive gear. I don't think you can put them on backwards. I know I said it had to be the drive gear but now I"m not sure what about the drive gear would make it so that. I know I'm not making things easier.

I had just learned about American cars in Sweden because I just shipped a 67 convertible over there. It turns out there are actually a bunch of American cars over there.

Gun Jam

it actually does make sense 67t5.

You can get left or right hand driven gears if I recall correctly.

If someone put the wrong gear on there I think that would cause the issue.

67t5ponycoupe

True, left hand or right hand driven gears but I was speaking of the drive gear which looks like it only come one way. If you put a left hand gear where a right had should go you will strip the gears. It won't drive it backwards. I have had that happen before. I am confident that is has to do with the gears I just can't work out in my head exactly what is going on to make the speedo work backwards.

Gun Jam

well if you ran a left hand set on a trans that requires a right hand set that should do the trick...

I know they sell LH and RH driven gears so I would think there are matching LH and RH drive gears.

urban_cowboy

A speed-o hole on the passenger side needs a LH rotation gear. A speed-o hole on the driver side needs a RH rotation gear...more or less. This is due to the direction the tranny shaft spins and what side the driven gear is on. I would not think you could get a RH driven gear to fit in a tranny that needs a LH gear...the gears cannot mesh. If yours will fit...I have to think that part of the issue might be a stripped or worn drive gear (they only come in one flavor for a toploader). Replace it and make sure you put in a LH rotation driven gear as the hole on toploaders is on the passenger side.

The only other thing I can think of is a broken tranny cable that is doing something strange when it turns in the reverse direction so that you see speed but will not turn when going forward.

Definitely strange.