Im pretty sure nearly every d21 owner has had this issue and I am about to tackle it. I found a supplier for the springs that snap in the seat. see link.
http://www.diyupholsterysupplies.com.au/page19.htm
You need the 9 gauge springs and the w clips are what I have purchased as they seem the...
Seems to be a common issue with Navara's as all 3 of mine have had this issue. On full lock it makes a screech noise like 2 pieces of metal with lots of pressure rubbing together. So has anyone figured it out what causes this?