Buying used Kenworth K125

Following its launch in 1971, the K125 quickly gained an enviable reputation for durability and reliability on long-haul interstate routes.

To fully understand the importance of Kenworth’s reliability during the young Australian truck manufacturer’s formative years in the seventies, it’s important to remember that many major trucking routes consisted of large unpaved sections of highway.

For instance, sections of the Eyre Highway linking Melbourne to Perth were still dirt until 1986, and the southern part of Stuart Highway, affectionately known as “the south road” linking Darwin to the southern states, had large dirt sections until 1987.

Furthermore, the K125 ushered in a new era of efficiency in Australian road transport, especially in linehaul applications. It boasted the most powerful engine offerings, was lightweight, relatively comfortable, and could be optioned with an integrated sleeper cabin.

But truth be told, it was the ideal big truck for situations where maximised load space could be achieved, even with the sleeper cab option and a bullbar. The K125 could tow a 12.5-metre trailer and fit with the day’s 17-metre overall length dimension requirement. Moreover, its practical design took into consideration ease of maintenance and allowed for quick roadside repairs, indeed winning its favour with owner-operators and fleets alike.

The K125 owed its light weight to an aluminium cabin frame with steel reinforcement in high-load areas. The aluminium and fibreglass panels are fitted using aircraft-type huck bolts and solid rivet construction.

The doors are an aluminium bulkhead design with continuous weather seals and full-length piano hinges that maintain precise alignment. Testament to this design is how nicely the doors still open and shut on this Mack Muncher even after travelling millions of kilometres.

The chassis comprises two straight constant-section frame rails that are custom drilled to suit the customer’s wheelbase, suspension, and other components to maintain frame strength. The frames were heat treated and die quenched. Forged aluminium cross members were employed to provide extra strength while keeping the weight low.

The cooling system piping employs only a straight section of rubber hose with corners and bends being achieved with metal elbows. This results in a stronger, more corrosion-resistant plumbing system that is simpler and less expensive to maintain than systems using preformed hoses.

Wiring and air lines are pre-assembled to length, tightly bunched and then routed high on the inside of the frame rail, away from bottom flanges where dirt can collect, and are secured every 100mm to eliminate chaffing. Furthermore, they are colour-coded for quicker maintenance.

When you start considering the standard features built into this model, it’s little wonder that the K125 model left an enduring influence on a young Mick Linger back in the early eighties when he started running across the paddock to Perth. But it was the infamous ‘Mack Muncher’ K125s that left a lasting impression.

Mick fondly recalls looking in his mirrors and seeing the faint glow of a headlight piercing the darkness in the distance.

“You knew it was a ‘Mack Muncher’ as those headlights quickly loomed larger,” Mick explains. “They were quick trucks, and they’d be out around you in no time. It didn’t take long for those red taillights on the trailer to disappear into the night either.”

Almost four decades later, Mick finally got the opportunity to purchase a unique piece of Australian trucking history when he acquired the Mack Muncher LT28 and the KAA-1 van from Cleveland Freightlines owner Frank Lenzi.

“When I first enquired about getting an original Mack Muncher, my one request was that the more stone chips it had on the front, the better,” Mick said

“My intention is to preserve the truck as a legacy to Frank and Cleveland Freighlines. I’m going to give it a good wash, paint the hubs and rims, clean the windows and Amor-All the dash just like a driver would before he’d head off on his trip.

“I’m not going to repaint it to concourse condition,” he added.

The K125 model boasted an extensive range of engine, transmission and final drive options. Mick’s K125, Mack Muncher, rolled off the Bayswater production line in 1982 powered by a Cummins NTC400 coupled to a Road Ranger RTO14613 (13-speed) transmission.

The rear suspension is Kenworth’s TBB-S-L44 torsion bar, which, even by today’s standard, is one of the lowest tare-weight rear suspensions in the industry. It afforded excellent articulation and roll stability.

Tyre wear was exceptionally good. Furthermore, its soft ride characteristics made it the preferred suspension for produce and express freight operators hauling fragile and sensitive freight. The rear axles are Eaton DS400P (with an oil pump) running a 3.7 ratio, which gave it a top speed of 126km/h.

“She’s got 3.5:1 ratio differentials in it now,” Mick said.

“For a truck that is over 40 years old, it’s in pretty good condition,” Mick explained. “I believe it was used as a yard truck, shuffling trailers in the last few years before I purchased it. But looking under the cabin, you can see how the mechanics worked on the truck to keep it going. It’s almost a living time capsule of Australian trucking in the early eighties,” he said.

Mick is keen to get started tidying up the KAA-1 trailer as he intends to take the K125 and its trailer on the run to the Alice Springs Road Transport Hall of Fame Reunion.

While the K125 model left an indelible legacy in Australian trucking history, chances are if you’re in the market for one, you’ll purchase it to restore rather than send it back to work. Frankly, though, if you are looking for a daily work truck, then better options are available. However, don’t underestimate a K125’s tenacity for a quick Tarcutta change-over.

While Mick has no intentions of sending his K125 back to work, he still loves getting behind the wheel and occasionally running a trailer to port with the old girl.

Nevertheless, if you intend to restore a K125, there is good news. Most parts are still readily available. But bear in mind that restoring a truck is not a cheap exercise. Understanding the Kenworth nomenclature, the ‘K100’ signifies a cabover, and the ‘25’ signifies a bogie drive on a torsion bar suspension.

When shopping around for a used K125, check that it is complete, meaning that it is not partially dismantled. If the K125 runs and can be driven, even with a permit, then that’s a bonus, as it will save on transport costs to get it home. But don’t be too quick to dismiss a partially dismantled K125, as they are often a good source of spare parts.

Truck Specs
Model: Kenworth K125CR
Engine: Cummins NCT400 with Jacobs engine brake
Horsepower: 400hp (298kw) at 2100rpm
Torque: 1450lb/ft (1965Nm) at 1650rpm
Gearbox: Eaton RTO14663 13-speed
Chassis: Single rail
Wheelbase: 4320mm
Air cleaner: Dual 16-inch Cyclopacs with raised air rams
Fuel Filter: Fuel Pro and fuel/water separator
Front Axle: Rockwell FF-931TW
Front Suspension: Multileaf
Front Brakes: 15x4
Power Steering: Ross HFB64
Rear Axles: Eaton DS400P (with pump)
Rear Axle Ratio 3.5:1
Rear Suspension: Kenworth TBB-SL44
Rear Brakes: 16.5x7
Windscreen: Two piece flat
Turntable: Jost JSK37
Interior: Crimson cab trim, HD diamond pleat vinyl
Seats: Charcoal HD Extreme air suspended driver’s seat
Bumper: Alloy bulbar
Battery Box: In chassis

1964 Kenworth K125 ($24,000)
1980 Kenworth K125 ($39,950)
1980 Kenworth K125 ($39,999)

(Correct at the time of writing)