[schuldiner]

positive the utes got 3.23's(except xr's) as thats what came in mine. i've just put in some 3.7's and i reckon my speed is out by about 15% and at about 110kmh i'm pulling 2,500rpm. this being an increase of about 300-400rpm(manaul) i couldn't see the 3.89's being more than another 50rpm. there is a calculator floating about i'm sure someone will pop in and give you a link. i purchased a new speedo gear for $12 from ford and the guy reckons every extra tooth on the gear is worth about 5-7% which sounds right as i was told to get the black gear which has i think 23 teeth as opposed to the grey gear with 21 teeth which is in my gearbox at the moment. i was told anything more than 3.7's in a non xr diff will involve modifications to the housing which will make it more expensive.