What is it about Nissans that make them unreliable?
Nissan vehicles just aren’t as reliable as Toyota, and that’s really a result of the Renault merger back in ~2000. The French don’t value quality like the Japanese automakers do. They use cheaper parts, and the overall quality just isn’t as good. That said, I own a Nissan Titan and I’ve been relatively happy with it, especially considering that it cost less than half of what I would’ve paid for a comparable used Toyota Tundra. I’ve had to do a considerable amount of wrenching to keep it up, but it’s paid off and I don’t have a lot into it and it’s never left me stranded.
I think the only relatively common issue I’m aware of with the Frontiers is that the transmission cooler will crack and cause coolant to get into the transmission fluid. Not sure which years have this issue exactly though. This is a problem with a lot of Nissan trucks and SUVs. The obvious fix is to put a better radiator/transmission cooler unit in before it happens. You can get an all aluminum one for <$400 probably and it’s not a very difficult job to do yourself. However, considering you’re looking at a standard transmission anyways it wouldn’t be a problem because I don’t think the standard transmission has a cooler.
Other common problems with Nissan trucks/SUVs include exhaust manifold leaks, catalytic converters that fail prematurely, relatively weak front suspension components, and rear diff failures. Not really sure if any of those apply to the frontiers, but I know they are all common to the Titan, Armada, pathfinder, and xterra based on personal experience and the experiences of friends who own them.
At the same time, I’ve talked to Nissan owners who have 200k on their vehicle with very little in the way of repairs. I purchased my Titan from a friend with 100k on it for $7500, and I’ve put about $4000 into it (including a set of tires). It now has 150k on it and shows no sign of slowing down. The engine is in excellent shape, the transmission shifts smooth, the AC blows cold, and I rebuilt the front suspension on it so it rides like a dream. That being said, I have friends who own first gen Tundras with 250k+ and they haven’t needed to do a fraction of the repairs I’ve had to do on my truck at 150k.The bottom line is that you can get them for a lot cheaper than a Toyota truck, but you’ll likely spend more money/time keeping it up.