1971 GTX with 4 speed and Dana 60

[71GTXdragpack]

Hi all,
can anyone tell me how to correct the speedo accuracy on my 71 GTX? I don't have a tach but when checking the speedo reading vs actual speed, I'm about 15-20 mph faster on the speedometer. Assuming I can change the speedo gear to gain accuracy? Also I have 255-60-15 tires that measure just over 27".
Any help is appreciated!

 

[Jerry Hall]

 

[0DegreeEngineer]

What is your rear axle ratio?

 

[71GTXdragpack]

What is your rear axle ratio?

3.55 and thank you!

 

[radical rob]

It is possible to bypass the problem all together. Speedtech makes a gps driven stepper motor that then drives your Speedo. Very accurate

 

[71GTXdragpack]

It is possible to bypass the problem all together. Speedtech makes a gps driven stepper motor that then drives your Speedo. Very accurate

appreciate the info but I'm a stickler for original. Will try and find the correct gear to correct the issue.

 

[BLK 68 R/T]

3.55 and thank you!

3.55 in a Dana 60?
Sure it’s not 3.54?

 

[71GTXdragpack]

3.55 in a Dana 60?
Sure it’s not 3.54?

you're 100% right, it should be 3.54...I was mislead by the chart...