Separate clutch faults from gearbox faults
Poor release can come from master or slave cylinder travel, air, worn pivots or clutch components—not automatically the gearbox. Note whether selection changes with the engine stopped, cold or hot. Oil specification and linkage wear also influence shift quality.
Trace vibration along the propshaft
The flexible coupling, centre support bearing, universal joints, alignment and engine or gearbox mounts interact. Mark shaft orientation before separation and respect preload procedures. A new centre bearing fitted around a binding joint will not cure the underlying vibration.
Ratio and differential type
Case tag, rotation count and internal inspection provide stronger evidence than a seller’s claim. Ratio changes alter acceleration, cruising speed and speedometer assumptions; limited-slip units also need the correct oil and condition assessment. Choose around engine, tyre and use rather than chasing a fashionable number.