Third gens had one heat exchanger and blower for the front, and a separate heat exchanger and blower for the back seat with its own controls - high/off/low fan speed plus variable heat setting. This worked awesome and would heat the cab up unbelievably fast even in single digit temps.
By Gen 5, which is a much larger vehicle, we got a single anemic (and noisy) blower fan up front pushing air through a single heat exchanger. Air for the back seat is piped from the front.
Needless to say this later method works less than 1/2 as well, but Toyota adopted the cost saving design up through the Land Cruisers, so it's firmly embedded at this point. But I no longer have a warm vehicle by the time I get to work on cold mornings.
Anyone who's owned multiple generations of 4runners will have noticed this same cost cutting trend in many different areas - from lack of locking gas caps and power antennas to only making the torsen diff available on the Limited.
I have a long list of things I miss from earlier generations, but the unfortunate reality is most current consumers care more about the infotainment package than pretty much anything else. And as a manufacturer if you can replace expensive hardware with dirt cheap electronics and keep your customers happy - of course you will. Plus those cheap electronics age out almost immediately thereby increasing the velocity of their customers' upgrade cycle. It's a win win win for Toyota.
