The A343F is in the same general family as the A340, but it is definately NOT the same transmission as the A340. The A343F uses much beefier internal parts. It's more related to the A341 series than the A340 series. The A341 being designed to fit behind the early V-8 engines of Lexus and others in the early 1990s as an upgraded version of the A340. The Land Cruiser A343F is stronger than any of the A340s out there. But the A340 series is still a good tranny.

The reference to the "bus transmission" refers to the A440F and the A442F series trannies. The A440F was used in the last years of the Land Cruiser 60 series and the very first Land Cruiser 80s (91-92). The A442F tranny was used in the 93-94 80 series. The switch over the A343F occured in '95.

The older trannies were directly related to a transmission literally used in certain Japanese busses, thus the term the "bus tranny" and they were MUCH, MUCH larger than the A343F. The change over to the A343F likely occured because Toyota figured that Aisin had sufficently beefed up the A34X series to meet the requirements of the Land Cruiser while being a much lighter tranny. And it appears they were right. Also some argue the A343F shifts smoother and drives better, probably related to its electronics than anything else.

While the A440/442 series is likely technically stronger than A343F, there's no evidence that the A343F isn't sufficiently over engineered for it's application that it can't handle anything anyone would throw at it. Including adding monster tires, lift and another couple thousand pounds of weight.

The A343F continued to be used in Land Cruiser production through the early years of the 100 series Land Cruisers. And 100 series was even heavier and more power than the 80. Which means they are heavier and more powerful when built.

The A440 transmission remained in production for overseas Land Cruiser well after 1992 and some have concluded this is because the tranny is better than the A343F, but the A343F is fully electronic and shares its brain with the engine ECU, so it cannot be easily adapted to diesel applications, thus overseas diesels remained with the older larger A44X trannies.