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Halda gearboxes

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Hi has anyone fitted a Halda Speedpilot MkIV to a TR3A?

The T gear box has threads that don't match the Speedo head cable.

Do I need to get a particular gearbox or can I rig something

With an new special cable if I can source the right cable ends?


Had anyone done this via say Speedy Cables

Or Don Barrow?


Or so I need a machinist to make me an adaptor?


I'm fitting the Speedpilot ins dummy glove box lid.

Will try and post a pic when I'm on my laptop.




Bill G@NB

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Hi Valvebounce!


Just to say Clive at Autochron was very helpful and

Sorted my out very speedily.


The right T-gearbox (between the speedo cable and the speedo head)for a TR2/3/3a/4 is a V12N which

Has an 8:1 reduction feed to the L-gearbox on the back

Of my Speedpilot( it has a built in reduction of 7:1)


Thus the revs to the Speedpilot are reduced by a factor of 60.


There are screw adjustments. On the base of the Speedpilot

To let you calibrate the built in odometer to an exact know distance

Ideally a 1mile or 5 mile bit of road that is that exact distance.

A SatNav or Garmin might help here and either put a mark

On a straight side road or a couple of pegs.


Once adjusted for a set of wheels/tyres no further adjustment needed

Except when on an actual really as I believe the organisers

Will nominate a marked stretch of road to be a particular length.


There is another adjuster in the Speedpilot which lets you trim

The final calibration to the organisers measured mile etc.


Next problem is to find a navigator! It might be easier


To find a driver though!




Bill G @ NB

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Hi Bill


did you bottom this out?


8:1 Gearbox on the Speedo and 7.5:1 "L" drive on the Speedpilot?


That is what I have but am struggling to get it set up. :D





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