What exactly is a transfer box clutch calibration and how would that affect gearchanges/shunt. I don't believe the dealer has even looked at this. The transfer box was removed from the car and resealed due to an oil leak but nothing more has been mentioned.

Basically, it's a diagnostic service function and can be a solution for driveline slack, judders and the like. The clutch controls the centre diff lock and the control module needs to be calibrated to the precise dimensions to function correctly - sometimes it can go out of calibration and will benefit from a re-jig. Takes a couple of minutes with an appropriate diagnostic tool (IID, Nanocom, SDD etc.).  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Harshness in the gear train could be the mechatronic unit. If the pressures aren't correct then there will be thunking etc. I believe you can replace solenoid valves in the unit. Problem with the mechatronic unit is that it's a big ticket item. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

The gearbox mechatronic unit has been replace under warranty already - it made no difference.

Hope you are not paying for this haphazardly way to find a fault. Not the way to go, even a LR warranty wouldn't pay up for changing bits to try and rectify faults. John

RRS MY12 SDV6 HSE. Sumatra Black/Ebony & Walnut + Dynamic Pack, + Cold Climate Pack + Memory Pack, Digital TV/DVD, Premium Leather, Cornering Lights, Cooler/Fridge Box, & most Options.

LR have been paying for trial and error fixes for 4 years - to no avail.