BLO GMH

i have an early 87 XF Fairmont Ghia and the speedo is out. it had a white 19 tooth gear in it which i understand is from a 2.92 ratio, however, the diff tag says it is a 2.77 ratio. so i take out the white 19 tooth gear and replace it with an 18 tooth purple gear (which bayfords in coburg told me was the right one) and it's still out!! here are the numbers:

P/N 82DA-4005-GC
Ratio: 2.77
Serial: 14581

can anyone help me?????

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- BLO GMH

-> 1987 XF Fairmont Ghia - Silver, 4.1 EFI, T5, LPG, Clive Cam, Megatork Valve Springs, Crow Pushrods, Crow Timing Gears, Pacemaker Headers, Hi Flow Cat, Mandrel Bent Exhaust, ESA Straight Through Muffler, Grey Velour Interior, Full Electrics, Trip Computer, MOMO Race Wheel, King Spring Super Lows, Monroe GT Gas Shocks, Nolathane Bushes, EL XR8 Rear Axle w/ 3.45 LSD, Snowflakes

WBT56

What is the error at 100km/h?

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If you're not driving a manual you're really just steering.

BLO GMH

when i was doing 60km/h, my old man was doing approx. 65km/p in AUIII, when i was doing 80km/h it seemed about right but then when i was doing 100km/h the AU was doing approx. 110km/h. so speedo seems to be registering low as compared to the AU

__________________
- BLO GMH

-> 1987 XF Fairmont Ghia - Silver, 4.1 EFI, T5, LPG, Clive Cam, Megatork Valve Springs, Crow Pushrods, Crow Timing Gears, Pacemaker Headers, Hi Flow Cat, Mandrel Bent Exhaust, ESA Straight Through Muffler, Grey Velour Interior, Full Electrics, Trip Computer, MOMO Race Wheel, King Spring Super Lows, Monroe GT Gas Shocks, Nolathane Bushes, EL XR8 Rear Axle w/ 3.45 LSD, Snowflakes

WBT56

Have you done a ratio check? If your car was actually running a 2.54 diff(don't laugh, they were available), this would generate the error you have. However, speedo error should be a constant percentage, and if it is not this usually indicates some damage in the system.

__________________
If you're not driving a manual you're really just steering.

yeah right

I'd check that the AU speedo is correct first - you got access to a GPS with an odometer on it? I used mine on my XF Ghia & it was spot on.