Let me elaborate a little bit.
If we focus on extended offroad expeditions or military use (rather than softroaders for mall runs or, at the other end of the extremes, rock climbing), then the modern automatic transmission has considerable advantages. Most military users today specify it.
- The automatic transmission is easier to use. This frees up driver attention to focus on track circumstances and choice of route. It reduces driver fatigue in difficult terrain that requires frequent up and down shifting.
- The automatic transmission has higher durability as it is more protected against transmission shock loads and driver misuse. Note that the FJ AT uses the A750 transmission from the 4Runner V8 (also used in Lexus GX, European Land Cruiser 120, or Toyota Land Cruiser Prado in Asia-Pacific markets), this is a very durable and proven transmission.
- The automatic transmission offers quick and seamless gear changes and a smooth torque delivery curve. This is a big benefit both when accelerating and when slowing down in difficult terrain with lack of traction.
- Probably less that can go wrong if you lend your 4x4 to a novice driver - as long as they are used to driving with an automatic transmission, of course.
There are also disadvantages, among them
- higher initial costs. For the 4x4 FJs the AT costs $410 more than the MT in spite of the MT also having a center diff. (This is just an example, there can be other explanations for this specific cost difference)
- in principle you wear your brakes more on an AT as engine braking can be poor. Correct use of the FJ's low range (L4) and transmission in engine braking settings (L, 2, 3, 4) can reduce this somewhat. (Again, the fact that the FJ 4x4 AT does not have a center differential restricts the use of low range for engine braking purposes - and/or increases shaft stress.)
The FJ 4x4 AT has a good coordination between transmission, range, diff lock, ESP, TCS and ABS, offering excellent offroad capabilities in combination with the right tires and some driver experience. So it is in this context that I state, that the "only thing missing" would be to have the option of permanent 4x4 (i.e. have a center differential) on the AT.
Just b/c the military uses something doesn't mean it's best....it may just mean it's easiest for troops to use and is bid the lowest by the contractor to build.
2nd, far and away, the manual transmission is a more reliable option than automatic. I've seen it enough to know.....if you have a problem with your AT, you will not be moving the vehicle. Often times, they will not even shift out of park....sure, I can disco both driveshafts and have it tugged off a trail, but on the trails I run, you can't be towed off the trail. You have to DRIVE it off.
By contrast, a MT can usually find at least ONE gear that still functions (usually more than one) and even if it's reverse, I can get it off the trail.
Then there's the issue of pull starting/roll starting a MT vs. AT....again, the MT has the advantage.
Then there's the heat issue.....ATs build huge amounts of heat that gear boxes do not.
There's the strength issue. Yes, the newer autos can be built strong, but if you compare apples to apples, you can build a stronger gear driven unit in the same amount of space.....you can even make it lighter than the AT in some cases.
The AT has advantages too....the torque converter is the biggest....acting as a cushion in the driveline and a torque multiplier similiar to 2:1 gear reduction.
The other thing, as Psychlone mentioned is seamless gear changes....a big plus when hitting a big wall at WOT.
The auto is now king in offroading....but the MT still has some advantages that make it a worthwhile consideration....just depends on what your biggest concern is: performance or reliability....and to be fair, if you choose the right auto (Powerglide for example) reliability is generally extremely good. However, that isn't really a fair comparison to what is offered stock for ATs in most vehicles either.
Ah...but who leaves anything stock? :lol:
Sean