Works on manual and electronic shift transmissions in heavy-duty trucks with 1-3/4 inch and 2 inch splined shafts. Tool is inserted through the inspection plate and onto the input shaft between the clutch brake and clutch forks. Tabs on spring-loaded tool fit securely between splines to avoid damaging shaft. Spring action adjusts to fit spline snugly. Align transmission by turning the shaft to line up with the clutch brake. Allows job to be done by a single technician.