For what purpose can shims be installed in various points during assembly?

Shims are used during assembly to achieve precise alignment and fit between components. In the context of manual transmissions, they can be installed for bell-housing face alignment, which is crucial for ensuring that the transmission aligns correctly with the engine and avoids issues such as excessive wear or vibration. Proper alignment helps maintain the correct distance between the transmission input shaft and the engine crankshaft, facilitating smoother operation and better overall performance.

While both alignment of the bell-housing face and block squareness are important in maintaining the integrity of the assembly, shims specifically address the alignment at the bell-housing level. Block squareness refers to ensuring that the engine block itself is flat and properly aligned, which is a separate consideration that does not involve the use of shims directly in the assembly of the transmission.

Thus, while shims can play a vital role in aligning the bell-housing face, they are not typically used for achieving block squareness. Therefore, the primary purpose of shims in the context of this question is specifically for the alignment of the bell-housing face.