Buying Used: Kenworth T408

When the familiar ring tone on my phone broke the silence, I promptly answered. It was a good mate from Townsville. After passing the usual pleasantries about family and such, he enquired if I had enough time to run a newly acquired used Kenworth T408 with a drop deck trailer he’d purchased in Melbourne up to North Queensland.

“It’ll make a great test run for one on your used truck reviews,” he added encouragingly.

After months of being cooped up in my home office, I promptly jumped at the opportunity.

This T408 originally came specked with a 550hp Cummins Cooled EGR-ISX, RTLO20918B 18-Speed Roadranger transmission. Eaton DS462-P rear axles were riding on a Kenworth Air-glide 200.

But first, we’d better explain what Cooled EGR is and how it came about.

As of January one, 2008, all new truck engines need to meet the ADR80/02 emissions standard.

Cummins chose Cooled EGR, which is short for Exhaust Gas Recirculation, for its ISX and Signature engines to meet the new standard.

According to Cummins, Cooled EGR is the most straightforward, most reliable emissions technology. Cooled EGR takes a measured quantity of hot exhaust gas, passes it through a cooler and then mixes it with the incoming air to the power cylinder.

Cooled EGR is an entirely self-contained subsystem on the engine. Interestingly it does not require any form of exhaust after-treatment, such as AdBlue.

Its simplicity is emphasised once compared with other emissions systems requiring multiple turbochargers, complex valve timing mechanisms, and elaborate plumbing.

Cooled EGR is a subsystem that also means that the proven base engine design and components of Cummins ISM, ISX and Signature engines do not change.

Another significant benefit Cummins claim of their Cooled EGR is that you don’t have to change gearing and driving style from older engine models to achieve the best fuel economy. While some other engine makers require their engines run is at very low cruise rpm for acceptable fuel consumption, Cummins EGR engines retain the same ‘sweet spot’ as their non-EGR engines. Cummins literature advises that driving an engine at very low cruise rpm compromises drivability.

In fact, drivers will notice improved performance with Cummins Cooled EGR, the brochure outlined. This is mainly due to Cummins’ patented Variable Geometry Turbo, which virtually eliminates turbo lag and provides a smooth, responsive powerhouse. But as these engines gathered a few miles under their belt, the VGT turbo often proved problematic.

Nevertheless, the responsiveness of this turbo is something that I indeed smiled about because of its immediate reaction. This engine has really performed well from the start, and it indeed hung on well on the long pulls. Meantime even along the hotter sections of the route, the pyrometer rose normally. Again, Kenworth’s engineers have done a marvellous job with this cooling package.

Both Cummins ISX and Signature engines continue to be the benchmark for retarding power, delivering up to 600 braking horsepower at 2100 rpm – regardless of their horsepower rating.

This is the same level as the industry benchmark established by the pre-EGR Signature engine. However, the EGR engines provide a significant improvement in mid-range braking power, to the tune of 75hp, and I’d have to agree as these new Cummins’ have terrific engine brakes, they are literally the most effective I ever experienced.

Meantime, Kenworth placed a lot of emphasis on enhancing the new T4 series model range for 2009. This new model range included a host of benefits for drivers, including cab dimensions that increased in height. In addition, the day cab version had been extended by 100mm, offering more cab space and improved accessibility.

The extra room in the T408 cab impressed me from the start and was one of the first things I noticed after coming out of the T404 a few weeks before. Even with the seat right back as far as it goes, there is still ample room behind it.

Another aspect of the T408 that impresses is the lavish cabin appointments previously only available in the T6 and T9 models.

At the launch, Kenworth claimed the T408 design “encompassed sleek styling, aerodynamic efficiency and fuel economy. The new larger hood and styling incorporates a new grille, new high visibility LEDs and repeaters, eye-catching aerodynamic new side fairings and full fuel tank fairing option along with new aero style bumper or FUPS compliant alloy bumper and bullbar options. With up to 550 horsepower options available, the T408 is the perfect truck for maximum capacity 19 and 26m combinations where overall length is critical.”

I was looking for a parking bay by midnight and found one just out of Narrandera. It was relatively full, and there were a few fridge vans at one end with general freighters scattered all around. Luckily there was a vacant spot at the far end away from the noise of the fridge vans. So I lay back in the bunk listening to the sounds of the night, owls hooting, crickets chirping, and the thumps of kangaroos hopping around the scrub for a few minutes before drifting into a deep sleep.

Sunrise the following day was spectacular.

An interesting point to note is that this Kenworth bunk comes standard with a full-size innerspring mattress, making for a great night’s sleep. In addition, the bunk’s doors can be opened to allow air to flow around the bunk, and the clip-on screens keep out all the insects.

An hour or so up the track, I pulled into the roadhouse at West Wyalong for a shower and cooked breakfast. Then, as a seasoned long-distance driver, it was time to dig in the kit bag for the elastic strap that I stretched across the bunk opening, which acts as a clothesline so the towel can dry while driving. Kenworth bunks have two convenient clips for just this purpose.

The comfort and handling of the Kenworth T408 were superb, especially given the appalling rough condition of the Newell highway. By nightfall, I’d made it to Goondiwindi, where I topped up the tanks with the cheapest fuel on the route so far, showered and ate before pushing on into the night for a few more hours.

I was hoping to make it to a large shady parking bay by the river Miles, which meant I’d have enough time in the work-diary to get into Townsville the following evening.

The standard 7-inch round headlights on the T408 are adequate, with hi-beam punching a brilliant bright wide beam into the darkness. The way the Kenworth dash illuminates at night is perfect. The gauges and back-lit switches make the driver’s environment all that much easier to operate.

As a used truck, the T408 is one model certainly well worth consideration because of its flexibility to adapt to a multitude of applications. Additionally, spare parts availability is not an issue with this model as most components, including cabin and dash items, are still used in production trucks today.

If this model has a weakness, it’s with early versions of the Cummins EGR engine. Thankfully as the engine model matured, its reliability improved. Nevertheless, the Cummins ISX EGR, like numerous other engines with EGR systems, is susceptible to typical EGR related problems. Here are three common issues you might encounter with a Cummins ISX EGR engine:

EGR System Leaks
One common issue is a leaking EGR valve which will cause a power loss and produce copious black smoke out of the exhaust.

While it is sometimes tricky to diagnose, you can monitor the engine’s coolant level to see if leaks are present. For instance, if the coolant requires an increase in top-ups than usual, it can indicate a leak in the EGR system. Another sign is if you notice white residue on the exhaust pipe from the burnt coolant. But EGR system issues are more commonly found in early versions of ISX engines, and hopefully, by now, a new upgraded ERG system is installed.

Flattened Camshafts
Notoriously, all ISX engines have had issues with their camshafts which are prone to flattening out.

Apparently, a problem in production with the rocker arms starved the components of proper oil lubrication, making them stick then hit the camshaft. Over time this will eventually cause the lobes to become flat.

Sadly, this problem is a little more challenging to diagnose as there aren’t specific symptoms that will indicate whether your engine may have faulty rocker arms. However, a drop in engine performance usually is one of the first indications of defective rocker arms.

VGT Turbocharger
The VGT turbocharger is one of the most notorious failures of Cummins EGR engines, and it is often expensive to fix.

While they are ideal for direct throttle response, as stated earlier in the drive report, VGTs often fail due to a build-up of carbon, soot, and other contaminants. As a driver, the initial telltale sign of a failing VGT is you may feel little or no response from the engine.

Realistically, the best fix is to replace it with a remanufactured unit.

But the good news is that Cummins did iron out most of those niggling problems over time. However, it is possible to retrofit a current model Cummins X15 engine, which essentially will upgrade your truck to a T409 spec.

Nevertheless, when it comes to a used truck, the T408 ticks so many boxes, from application flexibility to parts availably, it’s easy to see why they are very much a sort after used vehicle.

Specifications
Truck: Kenworth T408
Engine: Cummins ISX 550
Power: 550hp (410kW) at 1500rpm
Torque: 1850lb/ft (2508Nm) at 1000rpm
Gearbox: Eaton RTLO20918B, 18-speed
Clutch: Eaton 2250lb/ft Easy Pedal Advantage
Front axle: Meritor MFS 7.3t
Front susp: Multi leaf 7.5t
Rear axles: DS462-P
Rear axle ratio: 4.30:1
Rear susp: Kenworth Air-glide 200
Main driveline: Meritor RPL25
Inter-axle driveline: Meritor RPL20
Electrics: Power distribution box under sleeper
Brakes: Bendix ABS with traction control
Fuel: Alloy tanks, 4 x 450lt
Wheels: 10-Stud Alloy
Bumper: King-Bar’s Alloy bumper
Extras: 36-inch AERO-2 sleeper, Twin CR Turbo 2000 air dryer with heater, Jost JSK37 fifth wheel, Chassis checkerplate.

Here are a few examples we found at the time of writing:

2008 Kenworth T408
2009 Kenworth T408 AUTO 1 OWNER 950,000KMS
2009 Kenworth T400 Series