Rear axleCTN372

The CTN372 is a tandem axle with hub reduction,consisting of two spiral bevel single reductions and a trans-fer gear located in the forward rear axle.The rear axle is designed for a maximum engine torque of2400 Nm and is intended for heavy construction drivingor for heavy, long-haul transport with combined vehicleweights up to 100 tonnes.Tandem axle drive means that very high tractive force canbe transferred to the ground with no wheel spin, providingexcellent traction and low tyre wear.In hub reduction located in the hubs, a greater part ofdriving force is changed up. This means that the load onthe drive axles and the final drives is low. This offers highreliability even during extreme power-extraction or athigh speeds.The rear axle casing is manufactured from high-tensile,cold pressed sheet metal, which combines requirementsfor high strength and low weight.The CTN372 is fitted with three differential locks: one forthe forward rear axle, one for the rearward rear axle andone for the transfer gear. This guarantees good traction onslippery surfaces, increasing vehicle productivity.

The differential locks are easy to regulate by a two-stepswitch in the instrument panel. With the switch in thefirst position, the differential lock in the transfer gear isengaged, connecting both rear axles. The switch's secondposition connects the drive shafts of both rear axles.New production methods, combined with Volvo-approved special oil, has made it possible to extend oilchange intervals, leading to lower operating costs and alower impact on the environment. When special oil isused, the maximum oil change interval is 400,000 km orevery third year.

The following product features characterise the CTN372:• Two spiral bevel single reductions with high efficiency

and low service requirements.• Heavy-duty, hardened shafts and drive gears.• Hub reduction that reduces loads on the driveline.• Three reliable differential locks, which provide high

vehicle availability.

Specification

Designation .....................................................CTN372Type:Rear axle ....... Single reductions, spiral bevel with hubreductionTransfer gear ............................... Cylindrical spur gearHub reduction .................... Cylindrical planetary gearWeight, incl. driveshafts, hubs, drum brakes:Forward axle ...................................................... 775 kgRearward axle .................................................... 715 kgCrown wheel, diameter ................................... 285 mmDrive shafts, diameter ....................................... 45 mmMax. engine torque ...................................... 2,400 NmMax. bogie weight ......................................... 26,000 kgMax. combined vehicle weight ...................... 100,000 kgGear ratios:Gear ratios with hub reduction........................... 3.76:1

4.12:14.55:15.41:17.21:1

Transfer gear ........................................................... 1:1

RSP 403759.08.00. Eng. Printed in Sweden. Novum Grafiska AB

Fact Sheet

Oil capacity:Foward axle ........................................................... 34 lRearward axle ........................................................ 31 l

Rear axleCTN372

Differential lock engaged (rear axle)

Differential lock disengaged (rear axle)

Centre line, crown wheel - pinion

Tandem axle with hightractive force and good

traction

The CTN372 consists of two spiralbevel single reductions and a transfergear located in the forward rear axle.The function of the transfer axle is todistribute driving force evenly bet-ween the two rear axles.The driving force from the gearboxgoes via the transfer gear's input shaftto the differential. From the differen-tial, driving force is transferred parti-ally via a cylindrical spur gear to theforward rear axle's final drive, andpartially through the transfer gear'soutput shaft, which via a propellershaft, powers the rear axle's finaldrive.This type of rear axle combinationwith tandem drive makes it possibleto transfer a great deal of tractiveforce to the ground, without slip-ping, since the combined axle weightis high. This provides very goodtraction and low tyre wear.

Three reliable differentiallocks for high availability

The CTN372 is fitted with threedifferential locks, one for each rearaxle and one for the transfer gear. Thedifferential lock for the transfer gearconnects the drives of both rear axles,while the differential locks on the rearaxles connect the drive shafts withthe differential housing. When all ofthe differential locks are engaged, allof the drive wheels are forced torotate at the same speed.The differential locks consist of dogclutches of hardened steel that aremanipulated by compressed air. Twolamps light up in the instrumentpanel to indicate that the differentiallocks are engaged; one for the transfergear's differential lock and one forboth of the rear axles' differentiallocks.The function of the differential locksguarantees very good traction on slip-pery surfaces, resulting in high vehic-le availability.

Reliable final drives withsmall power losses

Both rear axles have spiral bevel finaldrives. This is a conical spiral spurgear where the pinion's centre linecoincides with that of the crownwheel. The spiral bevel gear is usedwhen the gear ratio between the pin-ion and crown wheel is small. It is asimple and easy-to-service design withsmall power losses.

Hub reduction with highreliability

The CTN372 is fitted with hub re-duction in each hub. Hub reductionconsists of a cylindrical planetarygear with straight-cut gears withneedle bearings, for minimal losses.The sun gear is mounted on the driveshaft, from which driving force istransferred to three planet gears thatare connected to the hub. When theplanet gear is forced to rotate againstthe ring gear, which is fixed in the rearaxle housing, a reduction of rotationspeed takes place. The reductionratio is 3.46:1

Single reduction in forward rear axle

Transfer gear in forward rear axle

Fact Sheet