GD Speedo sensor

[Glyn_Turner]

Does anyone know how many pulses per revolution the GD supplied (Motorcraft) speedo sensor that fits in the mechanical speedo drive of the Tremec gearbox puts out. Andy thought it was 8 but I think this is far too many.

Thanks

Glyn

[oglyoodoo]

I did some measurements on my GD supplied Motorcraft Speed Sensor a while ago when someone else on this site had a problem.

I don't know if there are different types but mine says on the box:-

P7AKA, W/O 185156, 072100

And on the side of the sensor unit:-

E9LF - 9E731 - AA

These are magnetic transducers so give pretty much a sinewave output consisting of positive and negative half cycles. As the output level depends on the rate of magnetic change the faster the thing spins not only do you get more pulses pro rata out but the amplitude also increases

One rotation of the shaft gives 8 cycles output ie 8 Positive Pulses and 8 Negative Pulses.

At 4 RPM mine gives out 32 Hz at 6V Pk to Pk (No load)
At 2 RPM mine gives out 16 Hz at 4V Pk to Pk (No Load)

So I reckon Andy is right for the above unit.

Denis

[Grease Monkey]

From what i recall when i set mine up, the logic went like this:

The wheel is 17" plus 45% of the 245 width as sidewall, times 2, so

Wheel Diameter = (17*25.4)+((0.45*245)*2) = 650mm

Wheel Circumferance is Pi x Diameter = 650 x 3.14159 = 2metres

A mile is 1600 metres, the wheel is 2m, so it has to turn 800 times per mile.

If you're running a 3.54:1 Diff, the propshaft has to turn 3.54 x 800 per mile = 2800 r/mile

I had to set my tremec sender unit to around 8500 pulses per mile, which corresponds to roughly 3 pulses per revolution of the propshaft.

Perhaps there's a 3 to 1 gearing in the sender drive, to it spins 3 times for every once at the prop ?