David P Posted April 19, 2011 Share Posted April 19, 2011 (edited) I have just changed from an N/A A340E auto trans with a 4.083 diff and 18" 35 275 tyres, to a T.T. auto trans with a taller 3.769 diff and taller 18 40 275 tyres. The speedo had been set with sat nav @ 70mph to suit the former gearing and the tyre change alone increases the rr by 2.5%. However, I have just been out to check against the sat nav with intent to reset the needle, yet to my amazement, a registered 30mph is 29mph and a registered 70mph is 70.5mph. Jackpot, if it aint broke, don't fix it, yet how can this be? Edited April 19, 2011 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
Gaz6002 Posted April 19, 2011 Share Posted April 19, 2011 The Supra over-reads as standard. Quote Link to comment Share on other sites More sharing options...
David P Posted April 19, 2011 Author Share Posted April 19, 2011 (edited) Nothing much is 'standard' any more, yet I had zero'd the U.S. spec mph speedo @ 70mph for the former gearing, so any change should show up. The gears are taller now, the sums say @ registered 70mph actual is 79mph, yet the speedo remains correct? Edited April 19, 2011 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
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