A: Automatic 3 speed
The 3-speed 727-torque flight automatic is an extremely strong automatic. This auto uses a lot of horsepower to drive the vehicle and the ratios are too tall in 1st and too low in 3rd.
The 4 speed ZF automatic is a lot more drivable auto than the 3 speed with a much better gear selection.
Note: The 4 speed Auto can not be put in front of the 3 speed transfer case as the ratios are very different in the transfer case.
B: Automatic 4 Speed
The 4-speed automatic has a great gear selection compared to any 3-speed auto. The ZF box is very reliable but doesn’t like heaps of horsepower in front of them.
C: Manual 4 speed
The 4-speed manual is a great strong gearbox. The gear shift is long and can feel like stirring a pot at times. The weakest link is the transfer case. Some kits were built in the past to rectify this problem but I believe due to the age of the gearboxes these kits are no longer available.
D: Manual 5 Speed
These boxes are OK. They do suffer from syncro problems around 140,000Km and need rebuilding to fix them. They are a small gearbox and can suffer in the 5th gear area as well. An OK choice but again if you are putting horsepower or torque in front of it you would have to treat it nicely. On the bright side the transfer cases are very strong.
D: 6 speed GM Automatic
The 6L80E is like the LS family of engines. It is the most commonly used engine / trans combo in the world. There are many many options available to strengthen the autos. As a factory auto they are better than every Land Rover automatic transmissions and with 6 speeds to cheese from, WOW.