Wherever it says "Jeep" think "Land Rover"

NV4500 Mythology

When the NV4500 was released in the mid-nineties, the 4wd aftermarket and magazines latched on quickly. It was uncritically ballied (sic) as the silver bullet and cure-all to any 4wd powertrain problem. Phrases like "Ultimate 4wd Transmission" have been common.

As time and trial have shaken things down, the NV4500 trend is now seen by serious 4wd powertrain aficionados as a prime example of herd instinct. Many individuals have been left unsatisfied with the expense of their transmission investment vs. its benefits. The drawbacks have been:

Gearing: The NV4500 has an initially attractive overdrive gear, but with a low gear of only 5.6:1 (most units) and a gear span of 6.07, its position against the heavy-duty four speeds (SM465, T18, SM420 or NP435) is inferior. Choosing the right axle ratio and tire size in conjunction with the right transmission is a smarter strategy than using overdrive as a patch to the system.

Size: The length of the transmission, even in its shortest renditions, is too long for many Jeeps, especially those with suspension lifts. The result is u-joint vibration and weakness. The transmission also often requires serious surgery of the body's tunnel to gain back ground clearance.

Expense: The initial flurry to get a 4500 drove up salvage prices that have never really ratcheted back down. New units have been available ranging from $2300. - $2600. Parts availability and expense are surprisingly discouraging in addition to frequent year-to-year parts changes. Expense for NVG to build these transmissions is significant. Overdrive adds serious complications to any gearboxes design and manufacturing.

Strength: Weaknesses in the transmission mainshaft clutch splines and their mating hubs (usually 4th & 5th gears) from fatigue and wear are prominent. The HD four-speeds exhibit consistently better strength & wear characteristics.

Adaptability: Expenses and complications in adapting to either the engine or the transfer case is high. Clutch linkages also prove challenging.

There are too many NV4500's in Jeeps due to an artificial push by aftermarket profiteers and hungry magazine writers looking for a quick story. Actual research and critical analysis by the thoughtful Jeep builder will more often yield the conclusion that a heavy-duty, four-speed transmission (if not an automatic) will produce better on-road & off-road results with significantly less expense.
There is an Advance Adapters Series t-case to SM465 adapter