Truck Transmission Parts Dammam

Start with the gearbox type plate

Mercedes-Benz, Volvo and MAN each fit their own gearboxes or ZF units depending on model, engine and year, and Sinotruk HOWO trucks commonly use ten- or twelve-speed manual gearboxes, including the HW series. Because of that mix, the model name on the door tells you very little. The type plate on the gearbox housing carries the gearbox type, ratio code and serial number, and a photo of it is the most useful thing you can send us. The chassis number lets us narrow the field, but the plate settles it.

Clutch parts: the wear item that sets the pace

A heavy-truck clutch kit normally includes the friction disc, the pressure plate assembly and the release bearing, and many workshops add the fork bushes or the slave cylinder while the gearbox is out. The disc diameter, commonly 395 mm or 430 mm on heavy trucks, and the spline count on its hub must both match, and the pressure plate must suit the flywheel and gearbox pairing.

Slipping under load, a high biting point, judder when pulling away and a burnt smell are the usual signs. Replace disc, cover and release bearing as a set, and have the flywheel face checked for heat spotting and scoring, because a new disc on a damaged flywheel fails early. On automated gearboxes the clutch position must be relearned after replacement with a diagnostic tool, or the new clutch will judder and wear quickly.

Inside the gearbox: shafts, gears and synchronizers

Synchronizer rings wear faster than gears, and crunching on one particular gear pair normally means one worn ring. The matching gear dogs and the sliding sleeve should be inspected at the same time, otherwise the new ring follows the old one within a few months.

• Input shaft, main shaft and countershaft, with the bearings that carry them.
• Gear wheels, sliding sleeves, and synchronizer rings and hubs.
• Splitter and range-change components on twelve- and sixteen-speed gearboxes, including their cylinders and seals.
• Shift forks, rails, linkage, shift cylinders and selectors.
• Oil pumps, oil coolers, breathers, pressure valves and seals.
• Gasket and seal kits, output flanges and end yokes.

Behind the gearbox: propeller shafts, joints and centre bearings

The drive line belongs to the transmission story, because a vibration that starts here is often blamed on the gearbox. Propeller shafts rely on universal joints, slip splines, a centre support bearing on longer layouts and flanges or end yokes at each end. A joint that has run dry develops play and knocks when you take up drive from a standstill, while a worn centre bearing produces a vibration at one particular road speed that fades and returns as the truck is loaded.

Grease the joints and slip splines at the intervals the manufacturer gives, and replace worn joints as a matched set. If a shaft is ever dismantled, mark the relationship between the yokes and the tube before you separate them, because yokes reassembled out of phase cause a vibration that no balancing will remove.

What long runs, port shunting and heat do to a gearbox

Tractors on the Riyadh corridor run at steady speed, which is kind to a gearbox, but in summer they do it at sustained high oil temperature. Gear oil that oxidises loses film strength, so the change interval matters more than the mileage suggests, and a blocked or leaking gearbox oil cooler deserves attention at every service. Logistics fleets and tractors making long runs rack up the kind of mileage where gearbox oil quality decides gearbox life.

Shunting is the opposite problem. Container and yard work around Dammam's seaport means hundreds of starts per shift, constant clutch slip and drivers forcing gears at low speed. That wears clutch discs, synchronizers and shift forks far faster than highway running does, so shunting tractors deserve their own, shorter inspection cycle.

Automated gearboxes: what changes and what does not

Volvo's I-Shift, Mercedes-Benz PowerShift, MAN TipMatic and the ZF AS Tronic and TraXon families are automated manual gearboxes. Mechanically they resemble a manual gearbox with a computer-controlled clutch and shift actuators, so shafts, gears and synchronizers are conventional parts. What differs is the actuator hardware, the sensors, the solenoid valves and the software.

We can match mechanical parts by type plate. Electronic modules and actuators should be matched against the chassis number, and any replacement will normally need programming or adaptation by a workshop with the right diagnostic equipment.

Gearbox oil, seals and the leaks that end gearboxes

The output shaft seal and the input shaft seal are the commonest leak points. A weeping seal looks harmless, but a gearbox that has lost a litre of oil runs hot and wears its bearings and synchronizers quickly. Check the breather as well, since a clogged breather pressurises the housing and pushes oil past the seals.

Use the oil grade and viscosity from the manufacturer's approved list for your gearbox type. A generic oil chosen on price is a false economy on a unit that costs so much to rebuild.

What to send when you order gearbox and clutch parts

Send a photo of the gearbox type plate, the chassis number and a clear picture of the worn part. For clutches, add the disc diameter and the spline count, and tell us whether the gearbox is manual or automated. We will confirm what we can supply before you commit.

Gearbox and clutch questions