Updated: Jun 27, 2021
This is going to be a very rough basis to go off of, there are a variety of different models among years and tons of little differences. I have driven every single Kei truck and most iterations of them, but far from all-knowing, so please feel free to suggest additions/changes/corrections. Please do not take anything personally if I “offend” your preferred brand with certain facts and opinions based on experience and existing information resources.
Mostly referencing 90-96 models as that’s most of what is available right now and when the format changed from 550cc to allow 660cc engines.
Daihatsu Hijet: 3 cyl. Daihatsu was slowly taken over by Toyota. This is a front mid-engine, right behind the cab, with a transfer case going to a front diff and solid rear axle. Climbers are 4,5 speeds with a manual transfer case high and low and diff lock. Axle lock is very rare (opposite to Suzuki where Axle lock is the norm and Diff lock is rare). Dumps are fairly common (both PTO "Power take-off" which uses the engine/transmission power to raise it and hydraulic which uses electric power to raise it). A/C can be found in some models (typically 5 spd). Automatics are very rare but more common than most brands. This is the only brand to have the JUMBO extended cab (which takes from the bed but allows even the largest of us to drive one. The front suspension only has a few inches of travel as such benefits from a lift. OEM ground clearance is middle of the road at 6.7”. Appreciated by off-roaders, while a bigger lift is needed for tall tires the wheel bolt pattern is the standard for ATV/UTV wheels at 4x110. 2”-3” lifts are common, with 3”-4” lifts for larger tires. While their body styles are fairly consistent (2 primary styles over the decade) they have 16 different engine configurations during the same period ranging from various Carb models, EFI (very rare) and even EFI Turbo (extremely rare). Horsepower ranges from 31-64hp and 23-50lbs/tq. EFI started in 1987 but was very rare until 1999 when it became standard. Top speeds can range from 50-85 mph depending on the configuration. This is a strut coil-over front suspension with leaf spring rear. These trucks tend to have electronic components like 4WD switches with vacuum solenoids which as a common issue can be known to fail due to age/lack of use. Easy to get parts for and known to be reliable. These were the most marketed at people looking for adventure but still commonly used across the platform carrying a long heritage with it (the first of these models starting in 1960).
Honda Acty: 3 cyl. This is the only truck that is a unibody, the body and bed are one unit. Some are 4spd and/or RWD. SDX is the most common style with Real (full) Time 4WD and 5 speed, many have A/C. The attack is typically 4spd w/ Extra Low gear and diff lock. Engine and transmission sit over rear wheels in a horizontal formation like a FWD car. Dumps are VERY RARE and in Japan their loads are limited to exclude dirt/sand since the weight is already so far back heavy loads can lift the front of the truck. Automatics are very rare. OEM ground clearance is tied for the highest at = 7.5″. The wheels are an extremely common bolt pattern 4x100 making finding street wheels super easy. For off-roading some kart wheels can be used, some may require a slight boring/modification to fit (since 4x4 isn’t the exact same as 4x100). These are less capable off-road in my humble opinion (sure I’ll get backlash for this statement). While the ground clearance stock is great, for serious off-roading there are too many sensitive parts close to the ground (even down-facing radiators/A/C compressors) also currently they are generally not lifted over 2”. Known to have the most complicated carb but you can still buy the whole assembly new. One thing some people may or may not appreciate is there have only been 2 core body styles over the decade (3 if you count the switch from orange to clear turn markers) and ONLY 1 ENGINE CONFIGURATION (E07Z Carbureted). This makes it easy to get parts for (and easier to get consistent information for repairs). It is also a fairly strong motor at 52 hp and 45lbs/tq. EFI started in 1996 with the Attack model but was very rare until 1999 when it became standard. The only thing that slows it down on the highway can be its full-time 4WD which keeps power distributed to all wheels when not needed. The 4x4 system is considered very reliable in these. Leaf spring rear suspension with coil front. Top speeds generally are 50-70 mph. While popular with consumers this was also a very common fleet vehicle especially in manufacturing and warehouses where they’d bring parts between nearby buildings. Acty’s are the youngest to the industry (1977). Acty’s are also the lightest of the Kei trucks coming in ~1476 lbs even with full-time 4WD. Also, if keeping in town Acty’s are surprisingly the highest-rated for fuel economy, however, if used on the highway their fuel economy is one of the worst and they can commonly burn oil when holding higher RPM’s for extended periods of time (this goes for all brands but especially Honda’s it seems).
Suzuki Carry/Mazda Autozam-Scrum: 3cyl. Suzuki and Mazda’s are the SAME truck. Primarily designed by Suzuki. They are similar to Daihatsu dynamics however the engines tend to be further forward under the seats in the cab (free heated seats in the winter). While the lowest ground clearance from the factory at 6.3″ these may be the most easily lifted and capable of big tires. The biggest restriction is models before 1995 had 114.3x4 wheel bolt patterns which can be difficult to find. Dumps are fairly common (both PTO and hydraulic), A/C is less common. A fair mix of 2WD/4WD and 4/5 speeds. Some models had an extra-low gear, others had full high/low gear ranges. Automatics are very rare. Opposite to Daihatsu Axle lock is most common. Suzuki’s can be found with Diff & Axle lock more than any other brand but still having both is very rare. These are commonly lifted 2" but can be raised even higher 3-4" lifts are not uncommon. Also opposite to Daihatsu, it’s the body styles that change the most on these (with approx. 6 style body over the same 10 year period) many of the body styles even exist together in the same year. A major difference between this and the other models is many of the components such as 4x4 and high/low transfer cases are mechanical as opposed to electronically engaged and very reliable. The older models had a supercharged option (very rare) and these and newer models have a turbocharged option (also very rare). The engine however has remained fairly consistent (F6A) with only 3 versions during this period and is one of the most commonly produced engines in Japan (and popular in Europe and the rest of the world as well) 36–63 hp 37–66 lbs/tq these engines are considered the most "capable" which these numbers support and are the easiest of the 90’s trucks to tune/modify with many aftermarket options available. FI started in 1985 but was very rare until 1999 when it became standard. Top speeds are typically 50-80 mph. These trucks are very easy to get parts for, many can even be found in NAPA and other auto parts stores (fuel/oil/air filters, alternators/carburetors/etc.). This is one of the longest most established brands of Kei trucks (coming in a close second having started in 1961) but possibly one of the most common being used across the market.
Mitsubishi Minicab: 3cyl Most similar to Suzuki (even sharing the same unique bolt pattern and many parts) but more “barebones”. These things were engineered with 100% simplicity in mind. Dumps are fairly common as is Automatic. A/C was a very rare option. No diff lock option made this less sought after as an off-roader. They can be lifted just as easily as the Suzuki/Daihatsu's. 2" common up to 4". Still, there are many variations including high roof models. There were 2 primary engine configurations (SOHC and DOHC) as well as 1 very rare turbo model (older versions were supercharged). They made 39-64 hp and 38-61 lbs/tq. OEM ground clearance is middle of the road at 6.7”. They also shared the Suzuki less common 4x114.3 wheel bolt pattern. Top speeds are typically 50-75mph. These trucks may be harder to get parts for than the other brands but due to their simplicity parts are less often needed and still fairly accessible even on US auto parts shelves. These were marketed as the affordable Kei truck option starting early in 1966. Their simple design also makes them the heaviest at ~1630 lbs.
Subaru Sambar: The only 4-cyl (not that this makes it more powerful holding the steady middle of the pack at 40-54 hp and 40-55 lbs/tq). The engine is the furthest back of any other model sitting behind the rear axle (the only engine to have a rear hatch to access the engine). All 660cc’s came as 5 spd w/ extra low. A/C was a fairly common option. Dumps were extremely rare (even more dangerous than the Honda Acty when it comes to heavy loads with rear weight, as such limited to exclude sand/dirt loads in Japan). OEM ground clearance is tied for the highest at = 7.5″ however lifts are not common due to their suspension style with 2" generally being the most people do. They also shared the 4x100 very common street wheel bolt pattern as the Honda Acty. Sambars had 2 body style configurations during this period (unless you count the limited “classic” style which would be a 3rd. There were 2 carbureted engines during this period and 1 supercharged EFI model (all of them known for oil issues) fresh gaskets and an oil cooler are recommended. The supercharger also runs hot, causing the ECU to dump fuel into the motor to prevent detonation, giving it terrible fuel economy (also can be fixed w a water-methanol sprayer). EFI did not start outside of the supercharged model until 1999. These are push button 4wd, some have diff lock optioned. While the 5 speeds offer a higher top speed potential due to the oil concerns its not recommended to drive for long periods above 70mph. Trailing arm rear suspension with spring and coil, coil-over strut front suspension. Subaru’s tend to be considered the least reliable (without proper maintenance) of the Kei trucks however parts are still common (while less common from Japan it may be the most US part conversion-friendly model). These were marketed to more to consumers carrying a passionate fanbase since 1961 (could be compared to the classic/modern VW community with their love of Beetles and Golfs).
Brad Lutz Sambar (inspiration of this post, the groundwork which I built off of in this post)
IN MY OPINION:
ALL OF THESE TRUCKS ARE AMAZING, in 4x4 mode, ALL WILL MEET 95% of ON AND EVEN OFF-ROAD (yard, trails, mud) DRIVING CONDITIONS. (4 spds can be less highway capible)
Off-road = Suzuki/Mazda/Daihatsu (for extreme off-roading get one with Diff and/or Axle lock). Suzuki/Mazda can generally have a larger tire with a shorter lift, Daihatsu generally needs more lift for the same tire but has a massive and inexpensive assortment of off-road wheels.
For the dump feature = Mitsubishi/Suzuki/Mazda/Daihatsu (PTO takes more skill/involvement but stronger than hydraulic)
On-road (without a heavy load) = Honda Acty/Subaru Sambar feel the most “balanced” especially in snow/rain.
On-road (and carrying heavy loads) = Daihatsu/Mitsubishi/Suzuki/Mazda. With the engines further forward you can carry a heavier bed weight and stay more balanced.
PSA: No matter what people say, while some tend to have more common qualities it is nearly impossible to make blanket statements that cover every truck based on brand alone. I.e., “Suzuki’s are better for off-road” well, no, depends on the configuration you are using and comparing it to…. same with “Subaru’s have the most interior space” well no… for example compare it to the Daihatsu Jumbo or even certain Suzuki/Mitsubishi interiors that are roomier (all depends if you’re talking about head, leg or foot space).
When it comes to things like top speed, this can be influenced by MANY factors (by the percentage of speed gained per each factor) such as body style, roof racks, lips, and lifts (aerodynamics). Wheel size/width (generally a taller tire means more top speed since you go further per rotation, but this only really applies to a certain extent and mostly on 4spds where the 5spds can run into power vs. drag resistance limitations (meaning a shorter tire may mean faster top speed). Driving conditions (up/downhill, surface type, elevation, and different quality/density air in different parts of the US). Expect a 4 speed lifted truck with roof rack wide tires, less powerful engine configuration, and a load to be considerably slower (especially uphill) than a 5 speed lowered narrow tire truck with good aero and a powerful engine configuration going downhill. ^_^
In any case, part of what makes these vehicles great isn't just their reliability, low cost of ownership, and functionality. It's how much can be done to make it specific to you and unique, just look at a few of these examples of these amazing little trucks in action!