Engine / gearbox problem

[Andy 1730]

Hi all hope someone can help ..my wife was driving the Alphard ...2.4 petrol auto ..she was going up a steep bank overtaking a slow lorry when the engine revved as if it was on kickdown and she lost all drive luckily she managed to coast into a pull in and now the engine is dead ..turn the key and it just clicks ..there's oil water etc ..is this an engine or gearbox issue ...thanks ..Andy 

[Picasso]

Possible speed sensors there is 2 on the transmission both the same part no. These alter the gear change 1st one does 1 and 2 gear change 2nd 1 3rd and 4th get ir read with diagnostic