Replaces the worn blocker rings in a GM NV4500 five-speed so second and third stop grinding and the shifter quits fighting you cold.
A Chevy or GMC three-quarter or one-ton with the NV4500 that grinds going into second or third, or fights the shifter on a cold morning and smooths out once it warms up, is almost always telling you the blocker rings are done. The RK4500A is the Chevrolet/GMC version of the NV4500 synchronizer ring set. It is built for the GM gear train from 1992 on, found in C/K 2500 and 3500 pickups, Suburbans and Kodiak-series trucks, and it is not the same ring set as the Dodge box.
The NV4500 is a cast-iron, top-loaded five-speed with every forward gear in constant mesh. Each shift slides a sleeve across a hub to lock a gear to the mainshaft. Before the sleeve can get there, the struts push a blocker ring onto the cone of the gear, and the friction between the two pulls the gear to mainshaft speed. Only when speeds match does the ring let the sleeve through. The gears in this box are stout; the rings are the wear item. Once a ring's cone face loses its grip, it cannot slow a spinning gear fast enough, and the sleeve teeth clash with the gear's dog teeth. Fresh fluid will not fix that, because the friction surface itself is gone.
A truck that suddenly loses 5th or makes a clunk in 5th is a different problem. Read the NV4500 5th gear nut guide before driving it further.
Grinding into every gear, including reverse from a stop, points at a dragging clutch or a weak hydraulic release, not the rings. Grinding that follows specific upshifts while moving is the rings. Our NV4500 synchro ring replacement guide covers the diagnosis, which rings fail first and why, and what to inspect once the case is split. Check what fluid is in the box too: a GL-5 hypoid oil poured in at some point is a common reason GM NV4500 rings wear early.
The RK4500A is for the New Venture NV4500 in GM applications, 1992 and up. Two things to check before ordering. First, make sure the case is really from a GM truck; NV4500s get swapped between brands, and the Dodge box takes the RK4500D Dodge ring kit instead. Look at the bellhousing pattern, input shaft and any case tag. Second, NV4500 ring sets come in five-ring and six-ring versions that do not interchange, depending on whether the box has a synchronized reverse, and some early GM units used an unsynchronized reverse. Count the rings in your box at teardown or send us the year, VIN and case tag and we will check it before it ships.
For what the whole job costs, see the NV4500 rebuild cost guide and our manual vs automatic repair cost breakdown.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. The GM and Dodge NV4500 ring sets are not the same. A Dodge Ram 2500 or 3500 NV4500 takes the RK4500D kit. If your transmission came out of another truck, check the bellhousing, input shaft and case tag to confirm which version it is.
It depends on whether the unit has a synchronized reverse. Five-ring and six-ring sets are not interchangeable, and some early GM units used an unsynchronized reverse. Count the rings when the case is apart, or send us the year, VIN and case tag before ordering.
Usually not. Grinding into every gear, including reverse from a stop, points at a clutch that is not releasing, a weak slave cylinder or air in the hydraulics. Rings fix grinding that follows specific upshifts, most often 2nd and 3rd.
GM called for Synchromesh manual transmission fluid in the GM NV4500. Do not use GL-5 hypoid gear oil, ATF or engine oil. Fill to the bottom of the fill hole with the truck sitting level.
Jumping out of 3rd under load comes from worn, tapered dog teeth on 3rd gear and the sleeve, not the rings. Inspect 3rd gear and the 3-4 sleeve at teardown and replace them if the teeth are rounded or chipped.
