I regularly drive a long winding downhill section in my XG auto ute, using the downshift to take the pressure off my brakes which get a real workout otherwise. Sometimes though I downshift and nothing happens, it just continues running all 4 gears like normal. Does anyone know why this happens and what I can do about it?

breaks are alot easier to replace that gearboxes - so why downshift? your putting stress on it that you dont really need to...

Engine braking won't cause any damage to the gearbox.

When moving the shifter into 3, can you blip the accelerator and then will it go into gear? It could be a case of the shift linkage being slightly out of position and only selecting the middle point between D and 3. Clould be a sticky solenoid, when was the gearbox last serviced?

Best guess is the Trans Range sensor - the sensor on the side of the gerabox (white) that tells the ecu what gear you put it in.

Common problem. Replacement from $90 upwards I think. DIY

Cheers

Nigel