CALIBRATED SHIMS FOR DIFFERENTIALS

Prometeo offers its customers a line of calibrated shims, necessary for the correct installation of differentials.

Prometeo calibrated shims are suitable for the following differential models: C510, C635, 4C, C530 and C630.

The following tables list the available shims, with reference to Fiat part numbers where available.

What are calibrated shims used for?

Differentials, both standard and self-locking, are supported by tapered angular contact roller bearings.

These bearings generally require a slight preload, as recommended in the installation manuals.

To achieve this, a shim of the correct thickness must be inserted into the seat between the bearing and the transmission casing (usually on the left side of the vehicle) to achieve the correct preload of the system.

The Prometeo differential installation notes provide the measurements to be taken and the formulas for calculating the correct shim value.The Lx measurement between the bearing seats, shown in the illustration above, is one of these.

When replacing a differential, it is essential to reset the bearing preload, as differential housings have slightly different measurements due to manufacturing tolerances.

Therefore, when installing a Prometeo self-locking differential, it is incorrect to use the same shims recovered from the previous differential assembly, since the Lx values are presumably different between the two diff cases.

Insufficient or no preload can cause differential malfunctions and premature bearing failure. On the other hand, excessive preload overloads the bearing, resulting in overheating and a shortened lifespan.

It is therefore essential that the differential assembly be performed by a professional mechanic to avoid malfunctions of the various components involved.