Daihatsu Hijet is not just a kei-car on FR-platform, but a whole subculture with a 60-year history. In this article, we remember the development of 4WD transmissions of Hijet-lineup cars from the moment they were introduced to the present day.
The first all-wheel drive Hijet was S66. Its 4WD type - dual-range part-time with a gear drive to the front output shaft.
Front differential - conventional, rear - free or optional LSD (friction type). Transfer control is mechanical by the lever. A year later, front freewheel hubs were offered as an option.
The next generation of Hijet / Atrai (S81-S83) was equipped with a several types of updated all-wheel drive.
Main type - dual-range part-time. Chain drive to front output shaft, vacuum servo for 2WD/4WD switching. Front differential - ADD type (right driveshaft disconnected for 2WD mode by vacuum servo).
Button on the transfer lever activates the four-wheel mode in transfer and ADD, the lever itself is used to switch low/high gear.
Second type - advanced 'all-time' (disengageable 4WD, with a center differential, single range). A bevelled symmetrical differential with mechanical locking allowed to drive in 4WD mode on any type of surface, while 2WD mode was intended for highways roads and fuel economy. Front differential - ADD, similar to part-time's one.
Button on the transfer lever activates 4WD and ADD, the lever itself is used to engage the center differential locking.
The rear differential could be either free or an optional 'super diff lock'. The locking is performed by another vacuum servo that moves the sleeve connecting the additional splines on the axle shaft with the splines on the protrusion of the differential case. Locking control - by the button.
Finally, an all-wheel drive version with automatic transmission appeared (micro van only): simple single-range part-time.
The next generation of Hijet S110 / Atrai S130V retained the same set of three 4WD types: part-time dual range and all-time for MT, part-time for AT.
The optional rear differential lock was moved from the right to the left axle shaft.
The design of the front ADD has been changed.
The transition to modernity (cab-over truck S210P/S211P and semi-bonnet microvan S210V) was marked by the rejection of the full-time AWD and the center differential.
MT versions had one of three 4WD types:
- Part-time (dual-range)(truck only). Front differential - ADD, rear - free or 'super diff lock'.
- Part-time (single range).
- Flex-4WD - a new single-range type with automatically connected front-wheel drive through a viscous coupling. Front differential - conventional, without ADD mechanism.
Daihatsu and Toyota classified this scheme as 'full-time', which greatly confused the catalogs and specifications: of course, this is not full-time AWD but the classic 'on-demand'.
AT versions had one of two 4WD types:
- Part-time (single-range).
Microvans Atrai S230V / Atrai Wagon S230G, Atrai 7 S231G and its rebadged version Toyota Sparky received the only Flex-4WD type without additional options.
Generation change of microvans Hijet Cargo S330 / Atrai Wagon S330G / S331G, the truck remained in the previous generation.
The design of 4WD has not changed, but the set of options was slightly different. MT versions had part-time AWD, single or dual range. The rear 'super diff lock' is only available for S210. AT versions still had either a simple part-time or Flex-4WD.
On the basis of semi-bonnet version of Hijet, the Indonesian department built a larger model (Daihatsu Gran Max) with traditional engines. In Japan it was rebaged as Toyota Townace/Liteace (S412/S413).
Real full-time AWD is used with a symmetrical bevel center differential and mechanical locking. Front and rear differentials are conventional free.
Center diff locking control - via vacuum servo.
Toyota that has never built a kei-cars previously, created 'Pixis' sub-brand and took a number of Daihatsu models for it, including Hijet truck and van, rebaged as Pixis Truck and Pixis Van.
The truck with MT had a single or dual range part-time 4WD, with AT - simple part-time. Front differential - ADD, rear - free or optional 'super diff lock'.
The van with both MT and AT had a simple part-time. Front differential - ADD, rear - free.
The illustrations show some details of the part-time 4WD control system: through the VSVs, the vacuum from the intake manifold or vacuum receiver is supplied to the actuators, which move the rods and sleeves in the ADD and the transfer case. Two more similar VSV actuate the rear differential locking vacuum servo.
Part-time 4WD diagram. 1 - VSV2, 2 - VSV3, 3 - VSV4, 5 - to intake manifold, 5 - check valve, 6 - 4WD position switch, 7 - transfer actuator, 8 - 4WD control switch, 9 - propeller shaft, 10 - 4WD indicator light, 11 - VSV1, 12 - front differential, 13 - front differential clutch, 14 - front axle actuator
Part-time 4WD components layout (van). 1 - 4WD indicator light, 2 - 4WD control switch, 3 - check valve, 4 - 4WD position switch, 5 - VSV3, 6 - vacuum tank, 7 - VSV2, 8 - VSV1, 9 - VSV4
Part-time 4WD components layout (truck). 1 - VSV3, 2 - vacuum tank, 3 - VSV4, 4 - VSV1, 5 - 4WD control switch, 6 - VSV2, 7 - 4WD position switch, 8 - H/L position switch, 9 - check valve, 10 - 4WD indicator light
Hijet Truck and Pixis Truck generation changed (S510), the microvan remained in the same body.
For MT versions single or dual range part-time was available, for AT - single range part-time only. Front differential - ADD, rear - free or optional 'super diff lock'.
4WD mode is intended for driving only on slippery surfaces, snowy roads, sand, rough terrain and slopes. It is prescribed to turn it on when the vehicle is moving straight and the speed is less than 80 km/h.
When the rear diff lock is on, it is not recommended to drive faster than 15 km/h.
Hijet Cargo / Atrai and Pixis Van generation changed (S710).
4WD for MT versions remained the same, but instead of a classical automatic transmission, a rather complex CVT introduced. In this case, 'on-demand 4WD' is used: the front-wheel drive is connected via electronically controlled hydro-mechanical clutch with 'locking' emulation. A notable feature of the CVT itself: for reverse driving, a geartrain is used directly to the secondary shaft, bypassing the variator pulleys.
Control - by a three-position switch (2WD - 4WD AUTO - 4WD LOCK).
For Hijet / Pixis Truck, which remained in the previous generation, a similar swap of automatic transmission to CVT was performed. Optional rear differential locking is available with both MT and CVT (an electronics appeared in the control circuit that switches it off and on depending on vehicle speed).
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