Am I correct in thinking I need 3 earth straps? 1.8 zetec/type 9 box

1. Battery -ve to chassis
   
2. Engine block to chassis
   
3. gearbox to chassis
   

I am sure someone will put me right, but I would say the battery to the chassis and the chassis to the block are a must, but as the gearbox and engine are metal to metal this will be a good contact anyhow so not needed.

Mark

As above, only 2 are really needed but an extra one onto the gearbox / engine assembly wont do any harm if you have the 3rd as i did in your kit. As you dont though you may as well just stick with two. The starter is bolted to the engine so earths through that.

Earth straps from Halfords. I would put one from starter bolt to chassis to ensure maximum oomph, and a second one from somewhere on the block or gearbox to chassis on belt and braces principle.

Without a strap there is a good enough earth to start my car via the grounding of the diff. (wouldn`t do this as it wont do the diffs ang good) Point is the gearbox wouldn`t need a strap.
However if the engine strap has a poor contact (corrosion), the gearbox one will start the car.

Darren

Note that you should never put and earth strap to magnesium.