Transmission repair is too complicated to be done in a garage. In addition to the need to remove and install very small parts, it is necessary to accurately measure various gaps and install shims of various thicknesses. Transmission internals are very expensive and difficult to obtain. Therefore, if there is a malfunction in the gearbox, we recommend that you take it to a service station for repair or purchase a remanufactured unit.
However, for an experienced mechanic, repairing a transmission is quite possible with special tools and fixtures, as well as when doing this job with great care.
To repair the gearbox, you will need pliers to remove the inner and outer spring rings, pullers for bearings, an impact tool, a set of punches, micrometers, possibly a hydraulic press. In addition, you will need a large workbench with a vise.
When disassembling the transmission, carefully mark all parts to be removed to facilitate subsequent reassembly.
Before disassembling the gearbox, try to find out the cause of the malfunction. Some transmission failures are related to certain components. Define these components (cm. "troubleshooting"), and the repair of the gearbox will be greatly simplified.