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speedometer adjustment defender td5


puiwit
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how can i adjust the speedometer at my defender td5?

is it electronically possible or does a transducer have to be exchanged?

i must adjust it because of larger tyres 35" and other axleratio 4.11.

i heard about a small box with an integrated circuit to fit into the speedometer-wire.

then you can easy adjust the speedometer by a potentiometer when you run different tyresizes.

who supply this box?

what did you do? :blink:

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... Use a GPS instead?

The mileage from a speedometer is useful to guarantee service intervals, but the speed can be tracked much more easily and accurately by GPS only.

And should you would ever want to sell the vehicle, the given mileage would be less than the actual mileage, assuming that you fit the larger tyres...

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Assuming your vehicle speedo is calibrated for 32" tyres (7.50R16 or 235/85R16) you should have:

Under-read of 32/35 due to tyre size = 0.914 x true speed

which will be cancelled out by the diff ratio which makes the prop spin faster:

Over-read of 4.11/3.54 = 1.161 x true speed

So the overall effect should be speedo reading of 1.06x true speed - +6% error which is probably acceptable isn't it?

There are different gears available for the speedo drive so if your vehicle has a gear suited to 7.50R16 you could try the one for 205R16 tyres but I think you will find it will then under-read which is illegal in some countries. Depends on how accurate it was to start with, so check it with a GPS to see the actual error % before you change anything.

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Guest diesel_jim

You could install the "VDO p/n 437-156 130 kph/ 85 mph 4" dia electronic speedo", it only goes up to 85 mph, but is fully calibratable (is that a word? :blink: )

you fit it, press a button, drive for exactly a mile and it sets itself up. ideal if you regularly change wheels over 'n' stuff.

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You could install the "VDO p/n 437-156 130 kph/ 85 mph 4" dia electronic speedo", it only goes up to 85 mph, but is fully calibratable (is that a word? :blink: )

you fit it, press a button, drive for exactly a mile and it sets itself up. ideal if you regularly change wheels over 'n' stuff.

Doesn't the sender cost several arms and legs? I use my old Garmin GPSIII which can be set on to 'big figures' for two data, so mine shows time and speed, very handy. Though as has been proved many times, a positional analogue gauge is easier and faster to read.

I bought my GPS for 2 cases of beer, cheap enough here :P

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Can't you just change the speedo gear in the transfer box ? I have fitted 4.11 R&P's to my discovery and Ashcrofts said they do different gears to bring the speedo back into line. Mines a 300 Series with the electronic speedo.

Ivan

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The TD5 is already delivering a pulse, so no extra cost.

So Jim, how does the calibrating work? Does the guage hold values for mileage or is that held in the ECU. I assume it would be a straight swap as existing TD5 guage is a VDO one.

Cheers

Steve

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Guest diesel_jim
The TD5 is already delivering a pulse, so no extra cost.

So Jim, how does the calibrating work? Does the guage hold values for mileage or is that held in the ECU. I assume it would be a straight swap as existing TD5 guage is a VDO one.

Cheers

Steve

I'm not sure how it works, the text i posted was from an ancient email off of the D90 source forum.

all i remember them saying was you had to push a button (i suppose its the trip reset one) and jiggle the ignition in some way to make it go into "learn" mode, then drive for exactly a mile (and i suppose press the button again to tell it you've finished the mile)

i suppose it must have in built brains that knows for one mile the speedo has recieved X number of pulses, and does its job that way.

kinda neat though.

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My speedo works by a transducer on the transfer box. This "reads" the speedo gear in the transfer box and transmits a pulse to the speedo. If you were to change the gear to one with more or less teeth would'nt this change the pulse rate from the transducer and so change the speedo reading ?

Ivan

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i suppose it must have in built brains that knows for one mile the speedo has recieved X number of pulses, and does its job that way.

kinda neat though.

Yeah must be the case, must count no. of pulses, i.e. revolutions in a mile and then can work out speed based on frequency of pulses. I like the idea of being able to reconfigure it with ease. I look at prices and they retail for £180+, so if I get one it looks like I'll wait until I go to US again where eguages have them for ~£60.

Thanks for the info

Cheers

Steve

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You could install the "VDO p/n 437-156 130 kph/ 85 mph 4" dia electronic speedo", it only goes up to 85 mph, but is fully calibratable (is that a word? :blink: )

you fit it, press a button, drive for exactly a mile and it sets itself up. ideal if you regularly change wheels over 'n' stuff.

They don't make that one anymore AFAIK. I wish they did as it is perfect for Canada.

You need to get the 437-155 (120 mph) unit or if you want km/h there are 200 and 300 km/h versions.

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  • 6 months later...
Guest diesel_jim

The plug comes as part of the engine harness (which plugs into the ECU), part n. AMR5725

however... the plug is exactly the same as the ones used on the back of the new type lights, namely the rear tail/brake light (3 pin) one.

these: 01253.jpg

so you could get an old plug with several inches of cable on and solder on some new bits, some heat-shrink and you'd hardly notice, or get the Little kits from vehicle-wiring-products (about 1/2 way down the page)

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