Speedometer Help

[REDCRO_REDNECK]

I have a 1987 v10 that came with 235/75/15s and 3.42 gears, It now has 4.10s and 285/75/16s is there a factory geat i can change in the tailshaft to get the speedo to read correctly?

Using the gear ratio calcs i seem to be 3 mph slower, can I get some confimation that I am not misreading them.

 

[89yimmiJ]

If there isn't. You can call a speedo shop and they sell speedo correction boxes. They go between the cable and tailshaft and allow you to calibrate to any gear/ tire combo. I paid about $75 for mine.

 

[dyeager535]

At one point I believe TCI had the information on their web site, to include selling the gears necessary to correct the speedometer reading.

 

[pauly383]

There is a calculator out there to do the math based on whether the case has a blue or grey gear in it , and it tells you what tooth count you need for the externally replaceable gear ..... then you can buy gears from TCI .

I ended up so far off with the gear and tire change I just got a GPS unit and drove around so I know what mph each step of my speedo really is