How to cure a stiff gear change on a Fiat Ducato motorhome or van

Fits fiat ducato peugeot boxer citroen relay glove box lid 2006-2011 grey peugeot boxer 2008 2.2 diesel. Peugeot Boxer 2011 2.2 Diesel. Peugeot Boxer 2011 2.0 Diesel. Fiat Ducato 2011 3.0 Diesel. Citroen Relay 2006 2.2 Diesel. Citroen Relay 2010 3.0 Diesel. Fiat Ducato 2007 2.3 Diesel.