Carraro final drive unit – Removing and install


Disassembling the Carraro final drive unit

Before draining the oil, position the wheel hub with the plug at its highest point and loosen the plug by several turns to release any internal residual pressure, then loosen it completely. Turn the hub again to position the plug at its lowest point. Completely drain the oil.
Loosen and remove the two planet carrier screws using a wrench. Extract the planet carrier from the wheel hub. Place the planet carrier on a workbench and check it for wear.


Replace the planet gears as necessary:
- extract circlip A from each planet gear
- remove washer B and extract planet gears D from their pins,
- recover bearings C and check their condition. It is recommended that you replace the bearings when installing new planet gears.

Disassembling the wheel hub

Before disassembling the wheel hub, it is recommended that you attach it with a belt or sling to a hoist or other suitable lifting device to prevent it from falling accidentally, risking injury to the operator and damage to the wheel hub. Some of the following illustrations may show axles that differ slightly from your model, but the procedure is the same.
Insert a lever between the swivel housing and slide it into the universal joint. Push on the joint with the lever in the direction of the final drive to remove the circlip more easily. Remove and discard the circlip. Remove and discard the washer. Remove and discard the two star washers.
Loosen and remove the screws from the ring gear carrier assembly.
To remove the ring gear assembly from its housing, screw at least two of the screws that have just been removed into the threaded extraction holes. While keeping an eye on the ring gear ports, avoid positioning the screws on the cast iron notches.


Remove the ring gear carrier with the epicyclic ring gear. Remove the snap ring and detach the ring gear carrier from the epicyclic ring gear. Check the condition of the parts. If necessary, remove the locating rings from the locking ring gear of the hub using a hammer and special tool, ref. CA715027.
Remove the wheel hub using levers and a hammer to facilitate the operation. Recover the bearing cone.
Place the wheel hub on a level surface and extract the seal ring (A) with a lever. This will destroy the seal ring. Remove bearing cups B from either side of the hub using a hammer and a suitable puller. Remove the bearing cone from the swivel housing side using a suitable puller. Remove the "O" ring C from the wheel hub.


Loosen and remove the screws from the upper and lower pivot pins. Before removing the pivot pins, attach the swivel housing to a hoist or other suitable lifting device with a belt or sling. Remove the pivot pins and recover the Belleville washers. Mark the positioning of the two Belleville washers, which are not identical.
Remove the swivel housing from the axle beam and the short shaft of the universal joint shaft. Place the swivel housing on a level surface and extract the seal ring with a lever. This will destroy the seal ring.
Turn the swivel housing to extract the ring using a drift and a hammer.

Dismantling the axle beam assembly

Separate the universal joint shaft from the axle beam.
Extract seal ring A from the axle beam with a lever. Remove the Belleville washers C from the pivot pin housings inside the axle beam. Mark the positioning of the two Belleville washers, which are not identical. This will destroy the seal ring. Extract ring B from the axle beam using a suitable puller.


Check the ring before reassembling and only replace it if its state of wear requires this.
Extract the upper rings D and lower rings E from the pivot pin housings F and pivot pins using a suitable puller.
Extract the nut and retaining washer from the taper pin. Remove the pin using a hammer.
Remove the pivot pin using a hammer or other soft object if necessary.

Reassembling the axle beam assembly

Install the ring of the upper pivot pin on the axle beam using special tool ref. CA715034 and a hammer. Insert the roller bearing cup on the lower part of the axle beam using special tool ref. CA715035 and a hammer. Cool the arm pins to under -100°C before installing them in order to facilitate their assembly. This can be achieved by completely immersing the arm pins in liquid nitrogen. To purchase or hire liquid nitrogen, contact the company "Air Liquide". It is advisable to wear protective gloves.
Install the ring on the axle beam using special tool ref. CA119055 and a hammer. Install the seal on the axle beam using special tool ref. CA119139 and a hammer. Fill the seal seating three quarters full with grease.
Lubricate the ring and the lip of the seal. Insert the universal joint shaft into the axle beam.

Reassembling the wheel hub assembly

Position screw A, nut B and washer C. If washer C is not fitted, the axle will be damaged.


Force Install the ring in the swivel housing using special tool ref. CA 119097 for 20.19 and a hammer or a press. Install the seal on the swivel housing using special tool ref. CA119139 for 20.19. Fill the seal seating three quarters full with grease.
Place the lower pivot pin on a workbench and install the ball joint cone using special tool ref.
CA715035 and a press. Apply a generous amount of grease to the pivot pin housings. Install the Belleville washers on the pivot pin housings.
Attach the swivel housing assembly with a sling. Lubricate the seal lip and protect the splined end of the shaft by wrapping adhesive tape around it to protect the seal from damage. After assembly, completely remove the adhesive tape. Install the swivel housing on the axle beam. Install the two pivot pins, one upper and one lower, and tighten the screws to the required torque using a torque wrench. Ensure that the Belleville washers remain in place.


The special "Set Right" operation, which consists of shimming the bearings, does not require any specific preload or setting. The required values should always be checked before installing new parts.

- A = 08.450 to 08.500 mm
- B = 54.775 to 54.825 mm
- C = 23.070 to 23.172 mm

Place the wheel hub on a workbench and install the two tapered roller bearing cups using special tool ref. CA715026 and a press or hammer. Insert the lip seal into the wheel hub using special tool ref. CA119143 and a hammer.
Install the bearing cone at the end of the pivot pin. Assemble the hub on the pivot pin and fit the second bearing cone.
Place the ring gear carrier on a workbench and ensure that the rings are flush with the ring gear carrier surface using special tool ref. CA715027. The two rings must be positioned slightly higher than the ring gear carrier surface to act as guide pins.
Pre-position the assembly consisting of the ring gear carrier and the epicyclic ring gear with special snap ring X, as shown in figure.


Install the ring gear carrier assembly on the wheel hub using the two shouldered rings as guide pins and tighten the corresponding screws until the ring gear comes into contact with the wheel hub.
Do not use the two screws that were used to remove the ring gear assembly from its housing when disassembling.
Force Install all the rings using special tool ref. CA715027 and a hammer. Install the ring gear carrier screws and tighten to the required torque.
Insert a lever between the swivel housing and slide it into the universal joint. Push on the joint with the lever in the direction of the final drive to remove the shaft and facilitate reassembly of the circlip.
Install two new star washers on the shaft. Check that the two washers are correctly positioned.
Install a new washer, positioning it so that the groove faces outwards.
Install the snap ring. Take care not to damage it during assembly.
Carefully push the universal joint and ensure that the circlip is correctly positioned in the groove of the washer.

Reassembling the final drive assembly

Recover all final drive parts.
Place the planet carrier on a workbench. Into the planet carrier pins insert: the lower bearings, the planet gears and then the upper bearings. Install the thrust washers with their circlips. Using a torque wrench, tighten the screws to the required torque.
Install a new "O" ring on the wheel hub. Install the final drive on the hub. Using a torque wrench, tighten the screws to the required torque.

Wheel alignment


Place two identical straight bars, each one metre long, along the sides of the ring gear and lock them on the wheel hub stud using two nuts.
Measure the distance M in mm between the ends of the bars. Keep the minimum value by oscillating the measurement point.


Ensure that the deviation in measurement A between the ends of the wheel hub diameters does not exceed the permissible values. Measured value M taken at the ends of the bars must depend on the ratio between the length of the bar and the diameter of the flange:
- Alignment (see chapter 8) = A0-2
- Measurement deviation = M0-5.
If the alignment is not correct, adjust the selector rails by screwing or unscrewing both tie rods equally, using two wrenches, until the alignment is within the permitted values.
Once adjustment is complete, screw the locknuts of the selector rails to the required torque.

Adjusting the steering angle

Use the bars fitted to adjust alignment and a long bar pressing against the machined part of the central body (gear side) so that the two bars form an acute angle corresponding to the maximum steering lock position.
Adjust the goniometer to the required steering angle and position it on the long bar.
Move one side of the ring gear to obtain the angle defined by the goniometer and formed by the ring gear and the long bar.
Adjust the mechanical steering stop by tightening or loosening the special screws, then lock them to the required torque using the counter-nut. Lock steering in the other direction and repeat this procedure.