Propshaft maintenance and component replacement on HGVs
The propshaft on an HGV transmits drive from the gearbox to the rear axle or bogie, often through multiple sections with centre bearings and universal joints. These components wear over time, accelerated by high mileage, heavy loads, and operation in conditions where the propshaft angles are at or near their maximum operating range during vehicle articulation.
Universal joints are the most common wear point. The needle rollers and cross trunnion wear, resulting in play in the joint that causes a low-frequency vibration at road speed and a clunk when drive is applied or removed. A worn UJ is identifiable by gripping the propshaft either side of the joint and checking for angular play. Any detectable play means the joint needs replacing.
Centre bearings on multi-section propshafts support the intermediate section at a fixed point on the chassis. The rubber mount in the centre bearing carrier degrades with age and absorbs vibration — a degraded rubber allows the bearing carrier to move and changes the propshaft angles, which accelerates UJ wear and causes vibration. Check the centre bearing rubber for cracks and deterioration alongside the UJ check.
Propshaft removal and UJ replacement require the vehicle to be safely supported under the chassis, the propshaft flanges disconnected at the gearbox and axle, and the UJ circlips removed before pressing the old trunnion out and the new one in. The correct UJ grease must be applied on assembly.
Frequently Asked Questions
What does a worn truck propshaft universal joint feel like?
A worn UJ causes a vibration that increases with road speed and a clunk or shunt sensation when drive is engaged or removed, particularly when pulling away from rest or changing gear at low speed. In advanced wear, the vibration can be felt through the cab floor and seat. Some vibration is also present when the propshaft is unbalanced — this is a different problem from UJ wear and requires professional balancing rather than just a UJ replacement.
How do I check if my truck's propshaft UJ needs replacing?
With the vehicle safely supported and the handbrake on, grip the propshaft either side of the universal joint and attempt to rotate the two sections relative to each other. Any angular play in the joint indicates worn needle rollers. Also check for radial play by trying to move the propshaft perpendicular to its axis at each UJ. Any detectable play means replacement is needed.
Can I replace a propshaft universal joint without specialist tools?
UJ replacement requires a hydraulic press or a suitable vice to press the old trunnion out and the new one in. An improvised method using sockets and a vice is workable if the socket diameters are chosen correctly. Circlip pliers are needed to remove and refit the retaining circlips. The job is within the capability of a well-equipped workshop.
Do I need to balance a replacement propshaft?
A new propshaft supplied as a complete assembly is pre-balanced. If you are replacing UJs on an existing propshaft, the shaft balance should not be significantly affected provided no material is removed from the shaft tube. If a new section or flanges are being fitted, balancing is recommended. If vibration persists after a UJ replacement on a shaft that was running cleanly before, a propshaft balance check is the next step.
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