Propshafts, or propellor shafts, to give them their full name, have a vital role to play in the life of a Series Land Rover. It is often not appreciated just how stressful their life can be and how important it is therefore to regularly inspect and service them. This is especially true when they are subjected offroad use.
The job of the propshaft is to deliver drive, via torque, from the gearbox to the differentials. Since the differentials are mounted on floating axles, then the relative positions of each differential and the gearbox change as the vehicle moves over undulating ground. Both the relative angles and the distance change and the propshaft has to be able to take account of this, whilst at the same time, delivering high values of torque from the gearbox. So next time you are ascending some serious slope in your trusty Series Land Rover and the windows are sliding themselves shut, spare a thought for those hard working propshafts and reflect upon whether you have given them the attention they truly deserve.
If you have not been paying due attention to your propshaft's welfare, then the first serious signs of impending failure are likely to be a rumbling sound coming from beneath the vehicle. The location of the sound may tell you whether it is the front or rear propshaft that is in trouble. This diagnosis may be easier if free-wheeling hubs are fitted and they can be disconnected to remove rotation from the front propshaft when in normal drive.
Sounds are common background noise in Series Land Rovers, but not rumbling sounds together with some vibration. If you experience this then they are probably propshaft related and one or more of the universal joints will need replacing. But, it could also be loose mounting bolts on the propshaft flanges, or damage caused after an offroading session that has lead to the propshaft becoming unbalanced. The sound is often best noticed when the vehicle is decelerating.
A worn universal joint can be identified by carefully inspecting for any observable movement between the flange yolk and the tube yolk (into which the UJ is mounted) when they are twisted relative to each other. There should be no observable movement at all, not even if a stout screwdriver is inserted between a joint component and a yolk and twisted.
Propshaft flange mounting bolts should always be checked for tightness (torque 35ft.lb. or 45Nm) and should have nyloc locking nuts (part numbers: II,IIA&III 4 cyl front and rear propshafts 3/8"UNF 509751) as they are constantly subject to vibration. It is also important that these bolts are of the high tensile variety and not standard specification bolts due to the high torques they need to endure on a regular basis (part numbers: II,IIA&III 4 cyl front and rear propshafts 3/8"UNF 1 1/8" long 509045; 1 7/32" long 509046). Early Series Land Rovers would have had Whitworth brand bolts, but nowadays UNF are the replacements offered.
It should be noted that 4-cyl and 6-cyl engines have different propshafts front and rear and that the rear propshaft is different for each of the three types of rear axle (Rover, Env and Salisbury).
The key to avoiding premature failure of the propshaft is greasing. This serves two purposes; the grease acts to lubricate the components of the UJ's and the sliding splined joint, but it also prevents entry of abrasive material into the joints and splines. So always ensure that joints are fully packed with grease whilst avoiding excess that could be thrown around through rapid rotation of the propshaft.
It is normal for the front propshaft sliding joint to be protected by a bellows-type rubber gaiter but not the rear one. Early diagnosis of a worn sliding joint is by checking for vertical movement of the joint - there should be none. Series Land Rovers have high ground clearance so there is usually no need to raise the vehicle off the ground to do the checking. If joint movement is detected then a replacement propshaft is required. Cheap versions are available but you only get what you pay for and cheap versions may fail in offroad use.
When propshafts are made their halves are assembled as a matched pair that are balanced under high rotation. If you dismantle a propshaft it is important to mark the alignment of the two parts of the sliding joint so that re-assembly will not affect the balancing.
It is often easiest to remove the differential end of a propshaft first. If it is one or more UJ's that are to be replaced then it's important to check their dimensions as there are two possible sizes. You need to measure the distance between the outer surfaces of the removeable UJ i.e. the surfaces that the circlips rest upon. Those distances will either be 2 15/16in or 3 7/32in.
When re-fitting propshafts it should be noted that it is possible to fit each of them
either way round. Normally however the front propshaft is fitted with the sliding joint nearest the differential to allow the rubber gaiter greater clearance, whereas the rear propshaft has the joint furthest from the differential to afford more protection from road spray.
Useful parts numbers:
Front propshaft SWB/LWB 4cyl - STC121
Front propshaft LWB 6cyl - STC574
Rear propshaft SWB - FRC4907
Rear propshaft LWB S11/11A 4cyl - STC573
Rear propshaft LWB S3 4cyl - 591279
Rear propshaft LWB S3 6cyl - 591283
Propshaft UJ (HARDY SPICER) - RTC3291GKN (earlier 2 15/16in type)
Propshaft UJ (HARDY SPICER) - RTC3346GKN (later 3 15/16in type)
Propshaft gaiter kit - 276484
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