Rebuilding gearboxes is a time-consuming and specialist task. Richard Simpson looks for cheaper, quicker alternatives

The days when truck transmissions regularly failed through driver abuse or poor lubrication are over. The 16-speed manual boxes of the 1990s have long been consigned to history. Most medium and heavy-duty trucks now have eight or 12-speed automated transmissions that are protected from driver abuse by carefully-written controlling software.

Many modern 12-speed AMTs no longer require synchromesh gears, as engine speed and road speed are so carefully matched by the controlling ECU that the pinions mesh perfectly on every change. Without synchromesh, a major wearing component is eliminated, and with it a source of lubricant contamination.

Similarly, the rise of synthetic lubricants has almost made truck gearboxes into a ‘fit and forget’ component, at least as far as the first owner of a truck is concerned, as drain intervals have been extended to previously unattainable intervals: 400,000-800,000km are typical for a premium heavy-duty truck.

But problems can still occur, often triggered by issues external to the gearbox. And current delays in the delivery of new trucks mean that fleets unused to running vehicles beyond the comfort of a three-year R&M package are now having to confront an unwelcome reality: everything wears out eventually, gearboxes included.

Rebuilding a worn transmission may be beyond the capability of a busy commercial workshop where the bulk of tasks are roadworthiness inspections and ‘pit-stop’ services. And even if the skills are there, will the individual who has them be left uninterrupted to get on with the job, or will this technician be called away to help colleagues with other tasks? How long can the operation wait until the transmission is pieced back together again?


A specialist company for whom transmissions overhauls are routine, could provide a cost-effective option. Step forward Peter Drugan, general manager of Truck Transmissions in Blackburn, a company that, as its name suggests, specialises in repair and refurbishment of truck gearboxes.

It has serviced a wide range of manufacturers’ product since its foundation in 1988, and was appointed to support Eaton truck transmissions 18 years ago when the company exited the UK, although that work has dwindled over the years as Eaton-equipped vehicles have disappeared from UK roads. Nowadays, Drugan says, most of its work is on Mercedes, Scania, and Volvo gearboxes, plus the ZF transmissions fitted to DAF, MAN and IVECO trucks. (Pictured above is a Volvo unit; Scanias are below and far right.) He says: “We don’t refurbish torque converter transmissions in-house, but we do remove and refit Allison and Voith units which are refurbished elsewhere.

“The truck market these days is a mix of automated-manual and stick-shift, with around 60% of our throughput being AMT.”

Age is obviously a factor: modern transmissions tend not to fail early and those that do are covered by a manufacturer warranty. Truck Transmissions actually undertakes gearbox warranty repairs for two truck manufacturers using their genuine parts.

The general manager adds: “We are starting to see gearboxes from 19-plate trucks, but most early failures are down to an external problem like a hose being broken. In most cases, it’s at least five years before failures present, although you do get occasional ‘new’ designs which can be problematic. It’s often something really basic like a spring clip failing, or a pin coming out and damaging the gearbox.

“Normally, the failure points can vary widely even on identical gearboxes doing similar work. Synchros are an obvious wear point. Many modern AMTs don’t have synchros, but software faults can cause serious mechanical damage.”

Truck Transmissions keeps some service-exchange units in stock, but this is getting more difficult. “We have less and less on the shelf, as some makes, Mercedes for instance, now have so many small variations. So we concentrate on quick-turnaround repairs. We have full garage facilities here for the removal and replacement of gearboxes, including three vehicle lifts, and our workshop can repair most transmissions in 24 hours.”

Drugan notes how work volumes are driven by the state of the truck market. He observes: “In 2008, everyone was buying new trucks and we saw a real downturn in work. Then came the financial crisis and people kept trucks longer so our work picked up. The current shortage of new trucks means we are seeing the same again.”


In the automatic transmission market, Allison Transmission has its own-brand remanufacturing service: Retran. Sean McGrath, channel and customer support manager, Allison Transmission, UK and Ireland, says: “The bulk of UK demand for Retran is from bus operators using the 1000 and 2000 Series transmissions.

“The Retran process sees each transmission stripped completely, and every component checked against new specification. Any item not up to spec is replaced with a new genuine Allison part. Clutch plates, bearings seals and gaskets are all replaced with new as a matter of routine.

“Additionally, the torque converter on the 1000 and 2000 transmissions is a non-rebuildable component, so this is replaced with a new unit.”

He adds that the transmissions are checked during assembly then dyno-tested to ensure they perform as a new unit would. And there is leak-testing, too.

“The Retran product is covered by a two-year warranty, and if the transmission has been installed by an Allison authorised distributor (in the UK, Mitchell Powersystems or Powertrain), then the warranty includes towing, and the labour for removal and replacement, too,” says McGrath.

“A 1000 or 2000 Retran unit will typically cost around a couple of hundred pounds more than one from an independent that may have been repaired with non-genuine parts. A Retran is generally 15 to 20% cheaper than the cost of an overhaul for a customer unit, and we have Retran units in all common specs on the shelf in the UK to get the vehicle back on the road as soon as possible,” the channel and customer support manager adds.

Retran units are built to the spec of the original transmission, but will incorporate parts from its final production iteration.

The Retran programme covers all Allison 1000, 2000, 3000 and 4000 transmissions, which started to appear in new vehicles from 2002. The predecessor MT545 units are not part of the Retran programme, and must be individually rebuilt, but, McGrath says, there are very few vehicles equipped with them that are still in service.

BOX: Factory refurbs

Many of the truck manufacturers active in the UK market offer their own refurbishment service or exchange transmissions. When surveyed, this is what they said:

DAF offers service exchange boxes for all applications. On average the savings are quoted at around 50% over a new box but some can be as high as 75%.

MAN remanufactures costly and major units for vehicles over four years old under the Ecoline brand. The cost savings for an Ecoline gearbox are 36% across the range of gearbox types.

Scania offers a range of OE-manufactured service exchange gearboxes and range change units, covering the entire range of trucks, buses and coaches. The cost savings compared with the new OE units are up to 60%.

Volvo rebuilds Refurbished Volvo Exchange Parts to the latest specification and sells them at attractive prices with the old component in part-exchange, it says. The warranty terms are the same as new genuine Volvo parts.

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