Help... what speedo ratio box do I use???

[BundyBrumby]

Ok, long story short...

My YN65 needs to be engineered for (amongst other things) the 33x12.5x15 tyres, to do so I must have the speedo must read correctly.
At the moment when the gps says the old girl has struggled up yo 100km/h the speedo reads 85km/h. I asked around different places and people but no body can tell me what percentage the speedo is out by. I cannot find a tyre placard anywhere on the thing so I don't even know what the standard tyre size is, so I cant use an online speedo calibration calculator bizzo.

Now please dont laugh... Am I correct in assuming that 100 - 85 = 15... Therefore its 15% out??

Has anyone used a ratio box on their hilux, if so do you know what ratio it was????

any help would be greatly appreciated

[91Mav]

Hey mate, you add the gearing to the original speed. Eg. For a 16.5% recalibration box - 85km/h x 116.5% = 99.025km/h on the speedo. Snake sell that ratio. Marks can probably get them too

[BundyBrumby]

Thanks very much for your help.... that makes much more sence I'll check them out now (and probably end up buying heaps of outer stuff whilst i'm looking lol)

[Elmo]

Been doing similar things myself. My truck has ended up the opposite die to deliberate overcompensation with the gearing, ie: speedo reads 100kmh but gps says 114kmh...

Anyway, marks said they dont care what its out by just figure it out, let them know and they will send you a box to suit your car..

sounded pretty good to me