LAND ROVER DEFENDER TD5 TDCI HEALTECH SPEEDO HEALER Fitting different sized tyres or a non-standard ratio ring and pinion in the diffs could well mean the speed displayed is inaccurate. Now there is a way to fix that problem!Fitting and programming this small box is easy. Behind the handbrake backplate, on later Defenders, is a green 3 wire transducer which generates a pulse. This is then sent to the speedometer to show your vehicle's speed. Once installed it allows you to adjust the output pulse, both up and down, which means your speedo will indicate the correct speed at which you are travelling. The instructions included detail how easy it is to program the box using a sat nav system. Suitable for.. - Defender TD5 1998-2006 - Defender TDCI 2007-2016 Contents / Part .