Single or Hub Reduction ? What?s the Diff??

Volvo recently released two new rear axles, the RTS2370A and the RT2610HV; both are the result of many years of experience and are characterised by their strength and reliability.

Volvo has a comprehensive range of drive axles for its new FH and FM models and operators can choose between single or hub reduction.

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Volvo?s new RTS2370A consists of two single reduction hypoid gears designed for an engine torque of 3100 Nm, and a transfer gear that is built into the forward rear axle. The maximum axle weight is 23 tonnes and the gross combination weight has increased to 70 tonnes rather than the 65 tonnes of the previous model.

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The RTS2370A comes standard with disc brakes on air suspensions and z-cam brakes on steel suspensions.

Volvo has designed its single reduction drive axles so that the hypoid final drive has the pinion?s centre line displaced in relation to the crown wheel?s centre line; this allows more teeth to mesh simultaneously. Having the load spread across more teeth contributes not only to added strength, but also to lower noise levels.

Drive from the two axles provides very high driving force as the total axle weight is high and gives excellent tractive force and low tyre wear.

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The Volvo RT2610HV is a tandem-axle with hub reduction in which the stepdown in rotational speed (torque enhancement) takes place in two stages ? final drive and hub gear. The two step process means that the load is split and is lower in each step.

The hub reduction consists of a cylindrical planetary gear with straight needle bearing gears. The sun gear is mounted on the driveshaft and the driving power is transferred from it to the three planetary gears that are connected to the wheel hub.

When the planetary gear is forced to rotate towards the ring gear, which is secured to the rear axle housing, there is a reduction in engine speed. The reduction in the hub is 3.46:1.

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The final drives of both rear axles are of the spiral bevel type. This is a conical spiral gear wheel where the pinion?s centre axis coincides with the centre of the crown wheel. The spiral bevel gear is used when there is little gear change between the pinion and crown wheel and is a simple, service-friendly design, with little loss of propulsion.

The RT2610HV has been designed for heavy, demanding transportation with loads up to 100 tonnes and can handle extremely tough operating conditions.

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Disc brakes are standard if air suspension is specified, drum brakes if steel suspension is specified.

The RTS2370A and RT2610HV are fitted with three differential locks; one each for the forward and rear axles in the tandem pair, and one for the transfer gear. This guarantees very good tractive force on slippery surfaces and increases vehicle productivity.

The differential locks are easily regulated with a two step switch on the instrument panel. Step one activates the differential lock for the transfer gear and couples both of the rear axles together. The second step locks the drive shafts of the respective rear axles together.

When all of the differential locks are engaged, all of the drive gears are forced to rotate at the same speed.

Rear axle casings in both models are cast in nodular iron resulting in a compact design and high ground clearance.

New design solutions and production methods, such as maintenance-free unit bearings, has resulted in extremely long service life and low operating costs. The bearing installation consists of conical roller bearings that are permanently lubricated. The wheel hub with bearings is fitted and removed as a unit to facilitate service and maintenance work. It is not necessary to adjust bearing play.