I have a 91 TA and just changed my wheels from standard 16inch to 18inch front 245 X40 and rear to 275 X 45. My speedometer is out by about 10 kilometers which is about 7 mph. It would be electronic speedometer. How is the best way to help make a change to compensate? I have heard there is a small box that can go inline with the speedometer wires to change the readings. Some help with this would be much appreciated. thanks.

 

This is what you need

 

Thanks. So this is just an add on to what is already there?

 

The box was primarily used to convert a 4thgen vss pulse to work with a 3rdgen speedometer but with all the factory 3rdgen vss speedo gears becoming obsolete this is a viable option to make the speedometer read right.
If you know what rear gears you have you might be able to figure out which vss gears you need and possibly find a set that can correct the speedo also

 

my son seems to think this correction box from Jaycar (Australia) may work?? What would you think?
https://www.jaycar.com.au/speedo-cor...odule/p/AA0376

 

Yep, just change out your drive/driven gear on your transmission tail shaft. If your drive gear (on output shaft) is a 15 tooth, you probably only need to change the driven gear (on vehicle speed sensor, VSS) to slightly a different tooth count. See PATC link below for reference.

https://transmissioncenter.net/shop/...ar-calculator/