4630 means early '90's maybe. How many hours? What's the overall condition....looking for neglect signs or properly cared for signs? Run it and shift it. Smooth; problems; probably synchronous so shifting should be smooth regardless of RPMs (assumption on this aspect).
Last year I bought an '88 3910 with the 8x2 with 900 hours. Tranny top cover gasket was leaking so in replacing, and doing the fluids changing at the same time, the gears in the tranny hardly had any contact wear, probably 20% of the face of the tooth is all that had the machining marks worn down.
If it's a show stopper, pop the cover and have a look. If you are serious and indicate that passing the inspection seals the deal, owner shouldn't mind you having a look. If he objects, take it as a warning sign.