Changing my speedometer from mph to km... what's wrong?

[3.0CS]

Hi all,

I am converting my USA spec 1974 3.0CS to European...

In the process, I bought a restored speedometer in kilometers in Germany and now that I installed it, I find that it is running way off... when doing 65 km per hour the speedometer shows 50.

Do I need to change a gear or something else?

Thanks!
victor

 

[HB Chris]

The speedo was matched to the differential ratio, what diff do you have? 3.07, 3.25, 3.45 or 3.64. US coupes in 74 had the 3.64, a lower diff will result in a low reading in the speedo. A good speedo shop can recalibrate your instrument.

Please add your location to your profile, it helps to know.

 

[OCCoupe]

There are 3 different calibrations from the factory. The easiest thing to do is to call Hollywood speedometer, ask them if they would calibrate the speed for you and then ask them for instructions on how measure your cable rotation. I just did the same thing on my car converting it to a kph speedo. If I am not mistaken they had me put a piece of tape on the speedo cable then push the car exactly 52.5 feet counting how many times the cable rotated. The tape helps you see the rotation of the cable. I then sent to speedo to them and they calibrated it to my car. I have used the speedo on my gps to confirm the accuracy. It is very accurate.

 

[3.0CS]

I have no idea what differential ratio I have, but I do know it is a 1974 USA model, so I guess it is the 3.64 mentioned.

Sounds complex! I will call Hollywood Speedometer....

Thanks!

Victor
Queretaro, Mexico

 

[HB Chris]

And there is a n umber on the back of your speedo with W=x.xx which tells which speedo you have.

 

[Markos]

I learned something new today? I'm ised to swapping speedo gears. I'm switching to kph also, but using the same donor cars diff.

 

[Stevehose]

Am I missing the latest trend? Is it the new thing to go KPH? Convert on the fly to know whether or not you're speeding? Living dangerously?

 

[OCCoupe]

Steve, you should really get with the times. A bunch of us are converting back to drums too.

 

[Markos]

Am I missing the latest trend? Is it the new thing to go KPH? Convert on the fly to know whether or not you're speeding? Living dangerously?

I want all things cool and different to put on my POS project car. That and I have very clean kph speedo. My car has a euro VIN, but looks to have been completely federalized.

 

[3.0CS]

Mmm... I learned a lot of new things... I have to take out my speedometer to check on numbers and find out what differential I have, then ask Hollywood speedometer to adapt it... not something I am looking forward too, but I do want it in kilometers.

Thank you all!

 

[Markos]

Will Hollywood adjust the odometer to match my old speedo? Otherwise I'll need to put it on blocks in my fathers garage and put the car in reverse

 

[3.0CS]

I just called North Hollywood speedometer and I was explained the process OCCoupe described.

I am getting ready to do it, but I just thought that first of all I need to check if the tire size I have is the correct one or not... if not, and since I am trying to return the car to stock, I would need to source appropiate tires before I do the speedometer adjustment.

I currently have 215/60/14. Is this the original size? The car has Alpina wheels.

 

[Stevehose]

195/70/14

I just called North Hollywood speedometer and I was explained the process OCCoupe described.

I am getting ready to do it, but I just thought that first of all I need to check if the tire size I have is the correct one or not... if not, and since I am trying to return the car to stock, I would need to source appropiate tires before I do the speedometer adjustment.

I currently have 215/60/14. Is this the original size? The car has Alpina wheels.

 

[3.0CS]

Ooops... so I will have to change tires before getting to adjusting the speedometer. Thank you Stevehose.

By the way... This is the car... I still need to remove the side reflectors before painting.

I

 

[Stevehose]

Only if you are going to keep the stock tire size (which are getting very difficult to find)?

so I will have to change tires before getting to adjusting the speedometer

 

[HB Chris]

195/70-14 and 215/60-14 have the same diameter, no need to worry.

 

[Bmachine]

Out of curiosity, unless you are going to Mexico or Canada, why would you want your speedo in KPH ?

I had my daily driver (which has a digital speedo) stuck in KPH for awhile and it was a total PITA...

 

[Markos]

Out of curiosity, unless you are going to Mexico or Canada, why would you want your speedo in KPH ?

I had my daily driver (which has a digital speedo) stuck in KPH for awhile and it was a total PITA...

I want KPH because my car (2204650) should have come with one as it was a euro car. It's different, it's interesting, and it's in better shape than my MPH speedo. I can generally tell how fast I'm going, but if I fail to read KPH I can download a free speedometer app on my Iphone.

 

[Stevehose]

It's about 2% off if that matters, I had 215/65/14's and they were 1% off but difficult to find.

195/70-14 and 215/60-14 have the same diameter, no need to worry.

 

[Stan]

195/70-14 and 215/60-14 have the same diameter, no need to worry.

actually 225/60/14 = stock diameter.