I have a 2013 Navara D40 auto with a very noticeable thud just a second after driving off.
The vehicle was still under warranty when first reported to our dealer and nothing was found when reported at 80,000 km service.
Now, at the 90,000 km service when the warranty has run out they are telling me the suspension is too soft and front and rear shockers and the rear leaf springs need to be replaced and they are not covered under warranty.
This seems very strange and I would like your thoughts on this.
The explanation you've been given doesn't sound right to me.
It needs further investigation and I would suggest you take it to a suspension specialist and have them give you a report on it.
Even though the warranty has expired I would believe you have a reasonable claim against Nissan on two grounds. First, you initially reported it while the car was still under warranty, and second, if the suspension is faulty as Nissan seems to be suggesting you could claim that it is unfit for purpose under our consumer laws.
That is providing you operate within the Navara's load and towing limits.