Repairing a manual transmission unit is a difficult job for the home mechanic. In addition to disassembly and reassembly, clearances must be accurately measured and, if necessary, adjusted by selecting shims. Internal transmission components are also often difficult to obtain separately, and in many cases are extremely expensive. Because of this, if the transmission is damaged or noisy, it is best to have the unit repaired by a professional, or replace the unit.
However, for a more experienced mechanic, it is possible to repair a transmission if the special tools are available and the work is done gradually so as not to miss anything.
Tools needed for reassembly: circlip pliers, bearing pullers, sliding hammer, fine-point punch set, test indicator, and possibly a hydraulic press. Also a large, sturdy workbench and a vice.
When disassembling the transmission, carefully note how each component is installed to allow for easy and accurate reassembly.