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Diff Gearing change means my Speedos out

Discussion in 'The Pub' started by spongesam, Apr 24, 2006.

  1. What i want to know is who can fix this?
    How much it'd be?

    My car is a VN calais 5litre auto

  2. Dude, get down to a Holden dealer's spare parts counter, tell 'em the new diff ratio and they'll sell you a new speedo drive. Replace current drive (should be in the gearbox), job done.
  3. If it's the bike you're talking about, you can get a "speedohealer" - they're advertised in the major bike mags and built for just this purpose.

    I think they're pricey though, so a lot of people either use a bicycle computer (cateye, that sort of thing) which gives a good accurate digital reading, or (like me) others just get used to how the speedo reads. Mine's 20% or so high.

    The one annoying thing is that since I changed the gearing like that, I've now got 20% "false" clicks on my odometer so my bike looks older than it is by about 5-10000 k. Annoying but not the world's biggest deal - especially if it means it gets new oil more often.
  4. I was going to suggest that too ... but thought maybe these days with "electronic speedos" etc that maybe they took the speedo "sensing" from elsewhere rather than it being gear driven off the back of the cogbox like they were years ago??

    When I was working in "spare parts" back in the *cough* um 70's :shock: it was a very common question. We needed to know what "box" the car was running .. what the diff ratio was .. what size rims .. what profile tyres etc .. it was a pain because the speedo gears were matched to the particular gearbox and the gears were just colour-coded. Like the "blue" gear went with the 3-speed Traumatic box .. the green gear went with the 3-slotter etc etc etc ... and none of the factory parts-books had "crossover" info ...

    I'd hope things have changed a bit since those days!!!! :LOL: :LOL:
  5. While I don't know about the OP's car (VN Commode), the VT series and onwards, at least, have a magnetic type sensor that is affixed to what we call a "bero" or a slotted part of the drive shaft. The slots affect the magnetic field as the shaft rotates and the pulses are counted. That way a speedo can work in reverse as well as forward.

    The OP, if he can, crawl under the car and have a look around the gearbox output to see if he can see any such sensors. They also use similar sensors on the wheels or hubs/half shafts for ABS and traction control.