Jaycar Speed corrector in Ford AU

Swap the gearbox sender to one which suites is much better.

IIRC there is a "screwdriver" adjustment in the AU. Maybe ask on a Ford forum, or at least in aus.cars

Hi all,

I've got an Ford AU3 Fairmont that has aftermarket rims/tyres. This throws the speedo out by about 10%.

I am trying to sort out whether a Jaycar speed corrector

Other issues may be shift points for the auto transmission and/or problems with cruise control.

I've hunted around the net looking for answers and came across a post where someone suggests that to control shift points it may require TWO speedo correctors. First corrector to drop the signal from the auto transmission to the speedo and the second corrector to increase the signal from the speedo to the ecu.

Can any of you electronic boffins shed some light on this for me.

I'm competent to assemble and install the kit but when it come to understanding electronics I'm lost.

Thanks for reading.

i assume it's much the same with drive running through an adaptor

Well ask ford first , I have used after-market from the valley in Brisbane

I supplied the required information and he came back with the righ adaptor

Sure, that's always an option but given that the rims and tyres fall within the legal size for my car, it's good to individualise a little...

Got a clue with regard to the question?

That's interesting, thanks for that.

In the past I've changed speedo gears in manuals but wasn't aware that a similar (if different) proposition was possible with auto's.

Can you elaborate a little as to where I'd chase it up and what I'd ask for when I get there?

(Is it simply a matter of saying that my speedo reads 10% high and could I have a speedo sender to suit, or is there more to it?)

little...

Probably cheaper and far more accurate to just use a GPS unit for speed readout. And if your speedo reads 10% high, your just less likely to get booked anyway! (are you sure it's reading high though? IF your tyres are bigger circumference it will read low. If they are lower profile and the same width, then they would be smaller circumference and you would be correct of course. IF they are both lower profile and wider, as is often the case with aftermarket "upgrades", then the circumference is usually not 10% different)

And the speedo reading has *ZERO* affect on your cruise control BTW. Are you really incapable of adding/subtracting 10% to the indicated speed when you set it?

MrT.

On Sat, 02 May 2009 14:01:55 -0700, Uncle Al put finger to keyboard and composed:

Isn't the sensor a 3-wire Hall Effect type, in which case the signal would be in digital form? Wouldn't it be wired directly to the ECU?

If the "someone" above is suggesting that the ECU should continue to see the actual speed of rotation of the transmission, regardless of road speed, then you would only need to connect the speedo corrector between the ECU speed output and the speedometer input, assuming the output is a pulse type.

This could be the kit -- Super Speedo Corrector:

- Franc Zabkar

On Sun, 03 May 2009 00:09:27 -0700, mark brothers uncle put finger to keyboard and composed:

If your car has an option for a lower ratio differential, then you could get the speedo sender that was designed to match it. IIRC, common ratios for other makes (in the 70s) were 2.92, 3.23, 3.50. These differ by about 10%.

Doing this, however, may change the shift points for your automatic transmission.

- Franc Zabkar

Thanks mate, appreciate your input. I rem your nic from the old a2600w days - glad to see you're still contributing :)

Well... a bunch of assumptions based on what?

If I only had one set of aftermarket rims in one size with one tyre profile and only drove it to the local shops then I may run with your line of thinking. That ain't the case.

Obviously a closer reading of my op would clue you in that I wasn't suggesting that the speedo reading *did* have any effect on the cruise control.

I don't know why whether or not I'd prefer my speedo to be accurate is worth you commenting about stuff of which you've no idea (my situation; my preferences; whether I have a gps; whether I have a clue about tyre sizes and speed differentials; at what speed I'm indicating a 10% difference; whether my calculating skills are adequate etc etc) but I guess if you've got time on your hands...

Got any input about Jaycar speedo correctors?