The most important thing when modifying a 4x4 drivetrain is ensuring it can handle the heavy forces of off-roading, towing, racing and similar applications. There are plenty of vehicles out there with the engine, driveshaft, axles and frame to do what you want — but the transmission is the weak point. The solution is upgrading to a heavy-duty transmission that’s built to be pushed hard.
The reliability of the NV4500 and AX15 has made them hot commodities in the DIY community. More than 30 years after these transmissions first appeared, they are still sought for swaps. However, you’ll need the right adapters to get the best performance. Advance Adapters has everything you need to know when choosing NV4500 and AX15 adapters.
About the NV4500 and AX15 Transmissions
First, here’s a quick overview of these transmissions and why they’re popular. The New Venture Gear NV4500 and Aisin-Warner AX15 are five-speed manual transmissions with a fifth-gear “overdrive.” The NV4500 uses a cast iron case and aluminum cover, while the AX15 case and cover are cast aluminum. The gear ratios are as follows:
- NV4500: 6.34:1, 3.44:1, 1.71:1, 1.00:1, 0.73:1, Reverse 6.34 or 5.61:1, 3.04:1, 1.67:1, 1.00:1, 0.74:1, Reverse 5.61
- AX15: 3.83:1, 2.33:1, 1.44:1, 1.00:1, 0.79:1, Reverse 4.76:1
The NV4500 was used in a variety of Chevy and Dodge trucks from 1992 to 2007, including GM 2500/3500 trucks and Dodge Ram 3500 trucks. The AX15 was used in Jeeps and Dodge Dakota trucks made from 1988 to 1999 with an AMC 4.2L 258 or Mopar 4.0L 242 engine. Visit our Tech Vault Knowledge Base for more information.
Adapters for NV4500 and AX15
When installing an NV4500 or AX15 transmission, many 4x4 owners are connecting it to a different engine and/or transfer case than it originally mated to. This means having the correct adapters and hardware for a secure, precise connection. Otherwise, instead of becoming more reliable, the drivetrain might well rattle apart. Depending on the amount of space underneath the vehicle, you may also need to modify the layout to fit the replacement transmission.
A typical NV4500 or AX15 transmission adapter package might include:
- An adapter plate to fit the transmission output to the transfer case input shaft.
- A bellhousing that will properly link the transmission input to the engine block.
- A new clutch slave cylinder and disc to disengage the clutch when shifting.
- A new crossmember and mounts to support the transmission.
- A shifter handle and linkage to shift the transmission.
- Upgraded transfer case output shafts and input gears to handle the added stress from the new transmission gear ratios.
- Assorted brackets, bearings, seals, washers, bushings and other hardware.
Above all, be sure you’re getting an adapter package made for your drivetrain. There are plenty of options to fit popular Ford, Chevy, Toyota and Jeep OEM components along with aftermarket Atlas transfer cases. Whether you’re using these transmissions to connect a GM LS and Dana 300, a four-cylinder Jeep YJ and NP231 or some other combo, there’s a good chance there’s a kit available. Just double-check compatibility and fitment before purchasing.