Steve Brooks reviews the Mack 60-inch sleeper, driving a Mack Super-Liner pulling roadtrain doubles.

This article has been republished courtesy of Trade Trucks.

Late in 2011, an invitation arrived to travel to Port Augusta to drive a couple of Macks up a stretch of the Stuart Highway. One a Super-Liner pulling roadtrain doubles, the other a Titan towing triples.

With the Super-Liner grossing around 80 tonnes and the Titan triple at a modest 110 tonnes or thereabouts, the performance of both trucks was nothing less than outstanding at the time.

Since then, I’ve driven a number of Super-Liners but the Port Augusta exercise was the last time at the helm of a Super-Liner in roadtrain configuration.

Until now!

New 60-inch bunk

The reason for this drive is the new bunk and there’s no question that even at first glance, Mack’s new 60-inch sleeper is quick to impress.

Sure, you still have the issue of no standing room between the seats but, with this bunk, it’s only one stooped step from the driver’s pew to a place where even big blokes have the space to stand bolt upright, stretch out, get changed, lay down, hang clothes, get something cool out of the fridge, and generally unwind after hours in the chair.

A word of warning though: take care when moving from the bunk to the cab. There’s a huge height difference and in the middle of the night when Nature calls, it’s easy to forget and knock the noggin; and knock it hard if you’re in a hurry.

Still, it’s bigger and better appointed than any bulldog bunk ever offered in this country and it’s no great surprise to learn that it’s actually derived from a premium Mack linehaul sleeper in the US.

Mack’s local team, however, was not about to take any chances with durability and build quality.

After all, it’s a sprawling bunk targeting the big end of the business where many long and often dusty days away from home are the norm, namely roadtrain, livestock and heavy haulage.

Consequently, it’s a sleeper which was subjected to two years of real world work and engineering evaluation before Mack ticked the ‘go’ box.

But more on the bunk in a little bit.

Engine and Transmission

While the 600hp MP10 has from the outset offered the choice of manual 18-speed and automated 12-speed shifters, the 685 comes with mDrive only.

Why? Well, there’s a big heap of torque coming out of the 685 and the automated shifter provides a higher, more consistent degree of driveline protection than a stick shift, particularly if the stick’s in heavy hands and the clutch pedal sits under an insensitive left foot.

A manual version is now totally out of the question. 

For starters, word has it that neither Eaton nor Mack have an 18-speed manual able to cope with the prodigious 2,300lb/ft torque output of the 685.

More significantly, however, is the recent release by Volvo of an extremely low geared crawler function for its I-shift transmission.

Right now, Mack isn’t saying when or even if the crawler option will become available on mDrive but with the Mack shifter based almost entirely on I-shift hardware, it’s easy to speculate that before too much longer the dog will be digging deeper than ever before.

Put simply, Mack would be crazy not to.

Super-Liner Performance

It’s early morning, mid-week at the new BP Westbound truck stop on the outskirts of Toowoomba.

The night before, an exceptional young man named Clinton Bridge from Nolan’s Transport in Gatton had hauled a dolly and pair of nicely detailed fridge trailers to a quiet corner of the truck park, coupled up and ready for the spanking new Super-Liner to slide under.

Taking the task upon himself, Bridge soon had hoses connected, landing legs up, checked all lights and confirmed that all clearances between truck and trailer were good to go. Top bloke!

With breakfast on board and the sun cracking the horizon, it was time to head 600km west to Charleville to overnight in the new ‘kennel’ before driving back again.

Standing on a 5.8 metre wheelbase and with a specification limiting gross weight to just 90 tonnes, the Super-Liner was on its maiden voyage and with two trailers in tow, performance and fuel consumption obviously weren’t expected to be at their best. Or so it seemed.

From the outset, however, the 685 made a mockery of two trailers and a gross weight estimated between 75 and 80 tonnes. Sure, it’s fair to suggest that’s exactly what a big bore engine dispensing 685hp and 2,300lb/ft of torque should do.

Yet even so, with mDrive’s tall 0.78 overdrive ratio feeding into a reasonably quick 3.73:1 rear axle – notching 100 km/h at a touch over 1450 rpm – the Mack’s tenacity and willingness to hold onto top gear was nothing short of awesome.

In fact, there were numerous times when the truck’s traits could be quite astonishing. Even disconcerting.

For instance, under light throttle at lift-off, it was not uncommon for mDrive to skip two or three gears in succession and haul away from as low as 900 and even 800rpm, well into the top half of the box.

Still, the outfit’s ability to simply grunt ‘n’ go at such low engine speeds was extraordinary and with the knowledge that the combination is programmed to perform in just such a manner, initial concerns soon dissolved.

Another plus is what Mack calls ‘Grade Gripper’. It’s dog talk for a hill start function and standard on mDrive, it makes uphill lift-offs immeasurably easier than using the trailer brake handpiece.

It wasn’t long before it simply became a pleasure to sit back, steer, let the electronic wizardry do its thing, and be impressed. And, as the kilometres kept clicking away, reflect on the reasons for Super-Liner’s evolution to top place on Mack sales charts. 

There was still an hour or so of daylight left by the time the Mack strolled into Charleville.

It certainly hadn’t been a hard day. The big dog just bowled along without raising even the hint of a sweat and according to the on-board trip computer, hadn’t drunk much either with a consumption rate of 1.7 km/litre, or 4.8 mpg.

By comparison, the return leg drew a bigger thirst of 1.5 km/litre (4.24 mpg) but much of that increase can be attributed to a few more hills, lots of stops and starts for video and photography purposes and an extraordinary amount of roadwork stoppages.

To my mind, both fuel figures are acceptable given that the truck was on its maiden voyage.

Bunk Performance

For starters, the mattress is 890mm (35 inches) wide and certainly comfortable enough for this body to enjoy a good night.

The only distraction was a hard head bang on the rear edge of the cab roof when I didn’t duck low enough during the ‘wee’ hours of the morning.

The Mack cab is, in fact, starting to show its age, with the complete absence of a stand-up option to complement the several tall sleepers already offered by the brand. Meanwhile, with air intake pipes impeding cab door opening angle, entry and exit are well short of ideal.

However, relief is on the way.

Word is slowly seeping out that an entirely new Mack cab which will tackle all current issues is now under development in the US.

It won’t arrive this year and maybe not next, but it is coming. On that, we’re certain.

Back in the big bunk, there’s plenty to like with a tall wardrobe cabinet between the bed and the back of the driver’s seat while on the other side there’s a 44 litre upright fridge with a slide-out work tray and drawer on the top. A TV was fixed to the wall above the fridge.

There are swing-out vents on each side and higher up on each side are sliding windows with mosquito-proof mesh and sliding curtains for privacy or just keeping the sun out.

Full-length curtains separate the bunk from the cab.

A single large hatch is on the driver’s side and personally, I think it’d be a good idea if this also had a mesh screen door for those balmy nights when it’s just nice to have a heap of fresh air. But without the bugs.

Another worthwhile inclusion would be a rack for a wet towel. It’s the little things that count.

Storage is plentiful with a large area under the bed, accessible from the inside by lifting the bunk and from the outside through wide locker doors on each side.

And while we’re on the outside, it’s worth mentioning the AdBlue tank.

Adapted from a locally developed Volvo design, it’s a 200-litre moulded container that sits inside the chassis rails and curves over the prop shaft with the fill nozzle tucked neatly under a swing-up access grate on top of the driver’s side rear fuel tank.

Whether it’s on Mack or Volvo, it is without doubt the smartest and most efficient AdBlue tank design in the business, leaving chassis space free to house emissions hardware and maximise fuel capacity.

What didn’t impress, however, was the position of the twin exhaust stacks behind the 60 inch bunk, particularly for livestock or fridge work.

In their present position, exhaust would be fed straight into the faces of top-deck livestock or the fascia of the lead fridge unit.

Mack is apparently well aware of the issue and says repositioning the stacks is not a major hurdle.


All up, the 685hp Super-Liner in this exercise was an absolute delight, delivering a superbly smooth mix of manners and muscle.

Yes, the cab’s showing its age with some aspects that aren’t up to scratch when compared with other premium brands.

Time and an entirely new cab will fix that in due course but when it comes to performance and technological harmony, Super-Liner sits at the top of the conventional tree.

As for the 60 inch bunk, its sheer size obviously precludes it from length-sensitive configurations such as B-doubles.

But then, it’s not meant for B-doubles and is unashamedly aimed at the biggest, heaviest end of the business.

For those roles it adds an entirely new and welcome dimension to Mack. Literally and physically.