I'm pleased to hear that you appear to have the problem sorted.
Regarding Rainbowj's query on Castrol synthetic gearbox oil, I used Castrol Syntrans in the late 1980's on the advice of a gearbox rebuild specialist. Castrol Syntrans was superseded by Castrol TAF-X (API GL4) and this appears to have been superseded by Syntrans Multivehicle 75W-90. If in doubt, refer to Castrol's website and lookup oils for Range Rover or Land Rover Discovery manual gearbox.
Personnaly, I have never and would never put ATF oil in an LT77 or R380 gearbox.
