NV4500 Transmission

Why We Love the NV4500

The NV4500 is one of the most versatile and proven 5-speeds ever put into a truck.

• Cast-iron case provides excellent durability

• Strong aftermarket support for parts and repairs

• Affordable to service — everything from synchros to main shafts is replaceable

• Works well behind anything from a stock 12-valve to a built compound truck

It’s simple, mechanical, and tough — exactly what a manual should be.

In the Cummins community the NV4500 is often the "whipping boy" of the manuals. There were approximately 20 times as many NV4500's manufactured compared to it's predecessor the NV5600. Some of the complaints about the NV4500 are definitely valid, but some are not at all (in our opinion)...

VALID COMPLAINTS

1. 5-speeds instead of 6: Honestly, a 5 speed manual is not always the most practical transmission for a diesel engine particularly when that engine is a 160 pump 12 valve Cummins with a very narrow power band. You have to rev uncomfortably high in 3rd gear to the point that the engine is being de-fueled and making little power just to shift into 4th and now be way under the power band once you've made the shift. Add a loaded trailer in the mix and it really isn't ideal. Because of this we believe that the BEST NV4500 modification (on a 12 valve truck) is actually a fuel pump mod; 3k or 4k governor springs.
2. 5th gear nut. 5th gear nut backing off is indeed a well-known issue with the NV4500. Is it as common as people make it out to be? Not at all in our experience. We build more NV4500's than any other transmission... roughly 5 minimum per week. Out of every NV4500 (which hasn't had the 5th gear fix) that comes through our shop needing an overhaul less 10% experienced that failure. That being said, the issue is very easily addressable at the time of overhaul. 

INVALID COMPLAINTS

1. "The NV4500 can't hold power". This couldn't be any further from the truth. The internals of the NV4500 are made out of the exact same 8620 alloy gear steel as the internals of the coveted NV5600. The gear thickness, diameter, tooth design, bearing load capacity, shaft diameters and treatment are ALL similar to an early NV5600. A simple affordable upgrade to the input shaft and your transmission will hold globs of horsepower and torque. People have a ragged out 2nd gen and get a synchro scratch, a leaking seal, a compromised shift fork and take to the internet to proclaim that the NV4500 "cannot hold power because my transmission failed at X amount of horsepower" even though those are not horsepower-related failures. Those types of failures can happen to any manual at ANY power level. 

At the end of the day we do not experience a legitamate discernable difference between the NV4500, NV5600 and G56 in terms of sending power through the transmission, however we will note that the wider distance between gears on the NV4500 does mean that you have to slip your clutch more in order to synchronize. Admittedly this does mean that the NV4500 is a little more clutch sensitive than the 6 speeds. Is a 6 speed a better candidate pound for pound when it comes to hooning? Yes. But the NV4500 is not incapable. A lot of our East Texas tractor pull rednecks absolutely prefer a NV4500 over anything else. Why? Because in that game they ALL are going to break eventually. It's a lot easier to maintain and/or replace a NV4500 than one of the 6 speeds 

We take pride in our NV4500's. 

Each transmission comes with a 12 month warranty that covers any builder's negligence associated with our work. If there's one thing that sets us apart in this market it is our willingness to stand behind our product. Competitors often refuse to warranty these transmissions even when they clearly advertise a warranty. We get it, it is hard to warranty a transmission intended for high-performance applications that get's abused on a daily basis. However, DON'T ADVERTISE a warranty if you refuse to help anybody that calls in with a problem. 

By making this purchase the customer agrees to send in core. Once the core is received and evaluated RoadRunner transmission will provide an additional estimate if necessary (for transmissions with excess damage). Once the build is completed the finished transmission will be shipped back to the customer. Please email for more information. We prefer to establish contact and set the table with our customers before proceeding with any build. We do not wish to sell you something that you do not need. Thank you