🔩 Thru Shaft / Through Shaft — Leyland L/L 3118 & L/L 3123
Component Type: Drivetrain thru shaft (also called through shaft)
Typical Fitment: Heavy‑duty Leyland commercial trucks — L/L 3118 and L/L 3123 models.
Context: This is an internal driveline shaft used in gearbox / intermediate shaft assemblies, transmitting torque from the gearbox to the propeller shaft and ensuring alignment within the driveline.
⚙️ What the Thru Shaft Does
A thru shaft serves as a splined torque‑transmitting shaft that runs through part of the gearbox, intermediate housing, or transfer assembly, allowing:
Smooth transfer of engine power from gearbox output toward the propeller shaft.
Spline engagement with mating components (yokes, couplings) so torque can be delivered even as the drivetrain moves under load or suspension travel.
Alignment and support — it often fits through bearings inside the gearbox or intermediate housing to maintain proper rotational axis alignment.
Unlike a simple propeller tube or secondary shaft, a thru shaft is integral to the powertrain’s internal mechanical path, not an external tube with U‑joints. It usually has precision splines and shoulders that fit bearings, couplings, or joint assemblies.
📌 Application in L/L 3118 & L/L 3123
Both Leyland L/L 3118 and L/L 3123 are medium to heavy‑duty commercial truck platforms, typically featuring manual gearboxes and multi‑section propeller shafts.
In these trucks, the thru shaft connects the gearbox output to the propeller shaft spline or intermediate shaft, acting as the main torque transfer path through the driveline.
It may also interface with intermediate couplings or centre bearings if fitted.