BUYERS GUIDE - HEAVY DUTY
It’s always amazed us that working-4×4 ute and light truck makers have stuck with manual transmissions, when all earthmoving gear and most heavy all wheel drive trucks have automatic transmissions. Thankfully, that scene is changing and there were three self-shifting light 4×4 trucks available in 2019.
The immediate choice is Isuzu’s market-leading Isuzu NPS300 4×4 that has just been released with the company’s automated manual transmission (AMT).
Another factory-fitted AMT 4×4 light truck will come from Iveco, in the form of the 2019 Daily 4×4.
There’s no official release date for this van and cab/chassis range as yet, but we reckon the Australian Iveco organisation is champing at the bit for the upgraded model, with its optional eight-speed self-shifter.
AMT models normally attract a RRP increase in the $3000-$4000 band.
The third entrant into the self-shifting 4×4 light truck market is Hino’s 817 4×4, but there’s no factory-auto-fitment for this truck as yet. However, there is an Allison after-market automatic transmission kit available from Penske and I was lucky enough to test drive the prototype vehicle.
First up, some background into 4×4 light truck two-pedal drivelines.
Why AMT and not full automatic
Isuzu and Iveco have adopted
automated manual transmissions for their 4×4 light trucks for two main reasons: lower cost than a torque-converter transmission and reduced torque
loading in the driveline.
Torque loading is a significant issue with 4x4s, because the transfer case low range ratio multiplies transmission torque by up to 3:1 in most cases.That’s a lot of torque loading going into propeller shafts, differentials and half shafts.
In the case of a torque converter automatic transmission, such as the Allison (left), there’s additional torque multiplication by the fluid coupling’s stator – typically 2.5:1 – and the transfer case may not have the torque capacity to handle that additional torque loading.
Most automated manual transmissions don’t have that torque multiplication. In the case of Isuzu’s NPS300 AMT that does have a fluid coupling there’s no stator in the coupling, so there’s no torque increase.
The Hino 817 4×4 is a different beast from its competitors, in that it employs the large transfer case from the company’s GT, 13-tonnes GVM truck, so there’s ample torque capacity in the transfer case to handle more than double the 817’s engine torque peak of 464Nm. Hence, it can accept a torque-converter