Duplex timing chain?

[Paulig174]

Hi my 2011 navara was hard started for awhile now.i changed the vacuum pump didn't work. Then it over heated one day so Ive it stripped down. Doing head gasket, thermostat,pump,etc and timing chain long
To make a long story short I just want to
know what year did navara start coming with duplex timing chains.i noticed mine already has one in it and I was blaming a stretched chain for my starting issues

 

[Old.Tony]

As far as I know, the upper chain has always been duplex, it's the lower chain that's been the problem (and it's the one that drives everything).

 

[johnl56]

Duplex for the cam and the lower is a single row chain.

 

[John.sas1]

From what I have read the duplex chain was discontinued after the common rail injection was fitted. I can't see that a stretched timing chain would make much difference to starting it. If the cam timing was out that far it would be causing other issues.