Carraro Front Axle – suspension


Disassembling the arm assembly

Lock the arms using a suitable lifting mechanism to prevent any untimely movement. Loosen the nut A and extract the taper pin B. Remove the pivot pin C using a rubber mallet or another soft object if required.


Remove the pin covers of the upper arms D at the front and rear of the arms, loosening the relevant attachment screws (F). Recover the seals and shims if present. Note the position of all disassembled elements. Remove the bearing G and the clamp ring H of each pin.


Remove the attachment screws I of the arm pins and extract the pins J using a suitable extracting tool inserted into the threaded hole provided in the pin for this purpose (screw M16 x 100).


Warning: This operation releases the arms.
- To make the extraction easier, the arm pin housing can be heated to a maximum temperature of 100°C.
- This operation will destroy the seals.
Remove the upper arms with a suitable lifting tool. Recover the seals and shims if present. Replace the shock absorber pads K if necessary by removing the relevant screws.


Remove the lower arm pin covers and the sensor E plate by loosening the relevant attachment screws F. Recover the rubber guide of the sensor.
Remove the attachment screws L of the arm pin bearings and recover the relevant thrust washer M and shims N, if used. The thrust washer fitted on the sensor pin has a special shape and must not be
confused with another washer. To reach the attachment screw on the side of the sensor, the mounting bush must be removed from the dust seal. This operation will destroy the seals. Remove the bearings O and seals P.


Remove the pins Q from the arms using a suitable extractor inserted into the threaded hole provided for this purpose (screw M16 x 100).


Take on the attachment screws to remove the lower cover T. Extract the axle beam cylinder.
Extract the O’ring U from the cylinder and the seal R from its housing in the axle beam. Do not replace the ring S unless necessary, using a suitable extracting tool.



Reassembling the arm assembly

Install ring A, previously smeared with Loctite 510, in its position in the control ram housingInstall the seal B on the axle beam and a new O’ring C lightly smeared with grease in the housing at the bottom of the control ram D. Install the ram in the axle beam.


Install the lower cover E on the lower part of the axle beam and tighten the relevant attachment screws to the required torque using a torque wrench. Before installing the cover, make sure that the O’ring is correctly positioned at the bottom of the ram.


Install the lower arms on the axle beam and align the pins by inserting special tool ref. CA715350 G into the housing at the side opposite the pin assembly. Install the arm pins H into the holes provided in the arms and axle beam, and push them home in their holes using special tool ref. CA715353.


Install one seal I onto each pin fitted in the lower arm housing using special tool ref. CA715352 and a mallet. Install a roller bearing J using special tool ref. CA715349. Install a spacer R (on the drive pinion side) of the correct dimensions (thickness: R=1mm) and install the thrust washer K fitted with the attachment screw L


The spacer outside diameter must be smaller than the bearing internal diameter. The thrust washer fitted on the sensor pin has a special shape and must not be confused with another washer. Shim the taper roller bearings by moving the axle beam arms and tighten the attachment screws to the required torque using a torque wrench.
Check the assembly position of the bearings on the arms. On the lower pins of the arms: the bearing must be fitted with the cup facing inwards (in the arm housing) and the cone facing outwards (on the pin). On the upper arms: the bearing must be fitted with the cone on the inside (on the pin) and the cup on the outside (on the arm housing).
Place a dial gauge with a magnetic stand on the axle beam and move the dial gauge feeler pin until it comes into contact with the face of the lower arm, then reset the dial gauge to zero. Install a lever between the arm and the axle beam, push the arm home at each side and measure the clearance using a dial gauge. Repeat this operation several times to obtain an average value X.


To determine the thickness S to obtain the required bearing preload, subtract the measured value X and the recommended value from the known reference value R:
S = (R - X) - V
V = 0.05 to 0.15 mm.
Select from the available shims the number required to obtain the thickness S defined previously.
Remove the attachment screws L on the gear side and the reference shim R. Insert shims S between the stop K and the taper roller bearing J. All shims must be inserted, and only on the drive pinion side. Reassemble the attachment screws: apply Loctite 542 to the threads, then tighten the screws to the required torque using a torque wrench. Repeat the described procedure on the lower arm.


Place the upper arms on a workbench with a suitable lifting device. If shock absorber pad P must be replaced, tighten the attachment screws to the required torque using a torque wrench.


Install the two rings Q in the pivot pin housings on the fork of the arm using special tool ref. CA715347 for models 20.22 S and 20.19 S, and tool ref. CA715385 for model 20.29 S and 20.43 S, and a mallet. It is advisable to cool the rings to a temperature below -100°C to make their assembly easier. It is recommended to wear protective gloves. Assemble the seals R using the special tool ref.CA715346 for models 20.22 S and 20.19 S and tool ref. CA715383 for model 20.29 S and 20.43 S. Install the spacers T on the internal side of the fork using special tool ref. CA715348 for models 20.22 S and 20.19 S and tool ref. CA715384 for models 20.29 S and 20.43 S, and place the corresponding O’ring U into the spacer housings.


Insert the spacer Z into the housing of the other pivot pin using the special tool ref. CA715364 for models 20.22 S and 20.19 S and tool ref. CA715384 for models 20.29 S and 20.43 S and the corresponding O’ring V. On the other side Install the dummy thrust washer W in the spacer housing using the special tool ref. CA715361 for models 20.22 S and 20.19 S and tool ref. CA715381 for models 20.29 S and 20.43 S. Check that the dummy thrust washer remains in position when assembling the arms, then replace it with shims after measuring the spacer clearance.


Using a suitable lifting mechanism, position the upper arms on the axle beam and link them to the lower arms. Fully insert the pins F in the housings provided in each arm using the special tool ref. CA715353. It is advisable to cool the arms to a temperature below -100°C to make their assembly easier.  Reassemble the attachment screws E. Apply Loctite 542 to the threads, then tighten the screws to the required torque using a torque wrench.


Install a seal H to each arm pin using the special tool ref. CA715351. Install a roller bearing I using special tool ref. CA715349. Install the cover J with its attachment screws K. Shim the taper roller bearings by moving the axle beam arms and tighten the attachment screws to the required torque using a torque wrench.


Place a dial gauge with a magnetic stand on the upper arm and move the dial gauge feeler pin until it comes into contact with the lower arm, then reset the dial gauge to zero. Install a lever between the upper and lower arm, push the arm home on each side and measure the clearance X between the bearings and their housings, using the dial gauge. Repeat this operation several times to obtain an average value.
To determine the thickness S required to obtain the required bearing preload, add together the measured value X and the recommended value V:
S = X + V
V = 0.05 to 0.15 mm.
Select from the available shims the number required to obtain the thickness S defined previously.
Repeat the described procedure on the other upper arm. Remove the arm pin covers on the gear side, Install shims S and a new O’ring L and assemble, filling their housing with grease and tightening the
attachment screws K to the required torque


Remove the covers from the side opposite the pinion, fill their housings with grease, then reinstall with a new O’ring L. Shims must be introduced on the drive pinion side. Tighten the attachment screws K with a torque wrench to the requested torque.
Align the arms, ram head holes and washers (if present). Special tool ref.CA715343 can be used for alignment of models 20.22 S and 20.19 S and tool ref.CA715382 for models 20.29 S and 20.43 S, but must be removed after the operation.


Simultaneously measure the dimensions X between the arm B and ram head C, and Y between the arm D and ram head C. Use two long shims, holding washers A in place. The minimum length of shims must be equal to the outer diameter of the ram head.


The clearance X must be at least 0.10mm. If not, move the shims S in the upper left-hand arm B across to the opposite housing of the same arm


The clearance Y must be at least 0.10mm. If not, move the shims S in the upper right-hand arm D across to the opposite housing of the same arm.


Install the locating pin ref. CA715343 for models 20.22 S and 20.19 S and tool ref. CA715382 for models 20.29 S and 20.43 S and adjust the components. Using a shim thickness Z, measure the distance between the spacer T and the dummy thrust washer W. Remove the dummy thrust washer, then extract the locating pin to remove the spacer housings located on the arms.


To determine the thickness S required to obtain the necessary clearance at the arms, calculate:
S = Z - V
V = 0.4 to 0.7 mm.
Select from the available shims the number required to obtain the thickness S defined previously:
Install the selected shims S and the spacer D in place of the dummy thrust washer using the special tool ref. CA715348.


Align the ports of the arms and control ram; insert the pivot pin P using special tool ref. CA751343, then fit it to the bottom of its housing. Keep the special tool at the opening of the pin housing. Lock the pivot pin with the taper pin Q and screw the nut R to the required torque using a torque wrench.
Extract the attachment screws from all lower arm pins and reinstall the assemblies, applying Loctite 542 to the threads then tightening the screws to the required torque using a torque wrench.
Install the seal M to the thrust washer of the sensor pin using the special tool ref. CA715345 and Install new O’rings in their housing on the covers O of the arms and on the plate N of the sensor. Install the arm pin covers and the sensor plate, fill their housing with grease and tighten the relevant attachment screws to the required torque.


Measure the distance Xac in Axle closed position between the pivot pin centre and the differential housing, choosing an exact reference point P.


Fully raise the axle beam arm and measure the distance Xaa in Axle open position between the pivot pin centre and the selected reference point P


Check that travel C of the control ram remains within the allowable limits, by subtracting the measured dimensions as follows:
C = Xaa - Xac
C= 88 to 89 mm
If the travel C of the suspension cylinder is not within allowable limits, measure the clearance X between the upper arms at the point of insertion of shims in Axle open position.


To determine the thickness S required for the correct end-of-travel position for the arms, add the measured value X to the recommended value V:
S = X + V
V = 0.3 mm.


Select from the available shims the number required to obtain the thickness S defined previously.




Lower the upper arms of the axle beam (Axle closed position) and insert the shims selected with their attachment screws. Lift the axle beam to maximum position again (Axle open) to position the arms correctly, then return to the initial position (Axle closed). Ensure that suspension cylinder travel C remains in the allowable limits.