clicking noise/gearbox

Just took the two spaniels to the vets and noticed a prominent clicking coming form the gearbox which only happens when i down shift from 5th to 4th.
Sounds expensive,any ideas

if you hear it only while you move the lever it might be from the selector bias, the most common is a crack in the plate(nr.6 in the link) Allbrit.de - Ersatzteile für LAND ROVER & MG ROVER ... but it can be bush nr 4 too, if you get there replace them both anyway, and springs 8, 9 too , all are cheap, it's important when you refit it to select 4'th and keep the lever max to the right while you tighten the plate retaining bolts to 25Nm otherwise there might be rough gearchange...see attachment

Think i owe you a few beers sierrafery,Thanks again

hi,
I think you'll find that it is the latch that prevents you going from 5th to reverse. As you come out of 5th and move across, the latch will release so you can pull back into 4th. I had the same issue on my manual Disco 1.
Absolutely nothing to worry about.
Cheers!