So, my ute is currently mostly stock, other than a disc brake strut conversion and a set of 13" mags, and after having a play with a brand new GPS on the way to work this morning I have discovered that my speedo is reading around 15% low.

Is there an easy fix for this? I am assuming that once the dogleg 5 speed goes in this problem is only going to get worse?

look up your closest speedometer service and have it calibrated... I think it needs to be pulled out of the dash but still attached... bit of a pain and fiddling, i pulled mine out and swapped it over for another one and its still not right, have been to lazy to pull it out again lol

Might be worth hitting up Nissan about the speed drive pinion, they are different colours depending on the diff ratio

Speedometer may be OK.

When you fit 13" tires to replace the stock 12", you change the effective gear ratio. Stock tires are 21.4" tall. What are yours (what size tires do you run)?

Even non-stock 12" tires can be 12% different.

155/80R12 21.8" (stock size)
165/70R12 21.1 (+ 3%)
185/50R13 20.3
175/50R13 19.9
165/60R12 19.8 (+ 9%)
165/50R13 19.5
205/40R13 19.5
165/55R12 19.1 (+12%)
175/70R13 22.6

To correct this, use a different speedometer drive gear (which bolts to the transmission).

The speedometer could also be out of spec. Do an odometer test and compare to KPH reading. e.g. one hour at 100 kph, does it read 100 km travelled? You can also get it recalibrated to be more accurate than stock (10% slow to 5% fast).

DD is right on the button and even worn tyres will give an inaccurate reading.
A quicker way to do an odometer check is to use the small green signs that give you the distance to the next town on country roads, like the one in the picture.


These signs are exactly 5km apart. Using the formula "Speed = Distance (km) divided by time (h)" will give you the speed.

Changing gearbox does not make a difference unless it has a different Speedo gear in it.

Being 15% low now, you could change the stock 17T gear for a 19T gear (Nissan special order). At least I think 19T would be closest or maybe 20T

yup its the 13 inch tyres my 120y reads slower with 13 inch aswell