NV4500 3rd Gear NV23712R, Dodge and Chevy 5-Speed

This is the third-speed gear for the New Venture NV4500 five-speed manual, Motive Gear part number NV23712R. It rides on the mainshaft between the 3-4 hub and the countershaft cluster, and it is one of the two gears in that box that actually wears out often enough to be worth stocking. The NV4500 went into Dodge Ram 2500 and 3500 trucks from 1992 through 2005 behind the 5.9L Cummins and the gas V8s, and into Chevrolet and GMC 2500/3500 trucks from 1992 through around 2001. The Dodge and GM versions of the case differ, but the third gear itself is the same machined part.

The failure this fixes is the classic NV4500 complaint: third gear pops out of engagement under load, or it grinds going into third even after the synchro rings and the 3-4 slider are replaced. When that happens the gear teeth and the dog teeth on the gear have worn tapered, so the slider gets pushed off the gear every time the driveline loads and unloads. New synchro rings alone will not hold it. You also see chipped teeth and spalling on the gear face on trucks that have been towing hard or that ran low on the correct 75W-85 GL-4 fluid.

On the bench: with the case split and the mainshaft out, press or drive the 3-4 hub assembly off, pull the old third gear and its bearing, and inspect the mainshaft journal and the thrust surfaces before installing. Replace the needle bearing and the thrust washer at the same time - putting a new gear on a worn bearing gets you back under the truck. Check third-gear endplay against spec after assembly, and reuse nothing in the synchro pack that shows a worn friction cone.

The NV4500 must run a GL-4 gear oil or the factory-specified synchromesh fluid. GL-5 hypoid oil attacks the brass in the synchronizers and is a common reason a rebuilt box goes back to grinding in a few thousand miles.