Thanks to Jeep’s legendary reliability, many vintage 4x4s are still found exploring off-road trails. Nevertheless, the powertrain may benefit from a few upgrades. In particular, a transmission swap can improve the drivetrain performance and make it more resistant to hard driving or impacts.
Replacing the original transmission with an NV3550 is a great way to get more years from your Jeep. In this guide, we’ll dive into how the NV3550 boosts performance and what to look for in an NV3550 retrofit adapter kit.
NV3550 Transmission Overview
As the replacement for the famed Aisin-Warner AX15 transmission, the New Venture Gear NV3550 was used in Jeep Wrangler TJ and Cherokee XJ vehicles from 2000 to 2004 with a 4.0L inline-six engine. This five-speed, longitudinal overdrive transmission has the following gear ratios:
- 4.01:1, 2.33:1, 1.39:1, 1.00:1, 0.78:1, Reverse 3.57:1
The heavy-duty NV3550 is essentially version 2.0 of the NV3500 transmission, which was coupled with 1990s GM and Dodge V8 truck engines. The only difference is that the transmission case and bellhousing come as separate pieces instead of a single unit. This allows more swap and upgrade possibilities while maintaining the ruggedness and versatility. It’s a great transmission for many classic Jeep models, including the Jeep CJ, Comanche MJ, Wagoneer XG, Gladiator SJ and Wrangler YJ. You can adapt to other 4x4s as well, like the original Ford Bronco. Or get them as part of a more comprehensive Jeep overhaul, such as putting in a GM LS engine. Find more information about the Jeep NV3550 in our Tech Vault Knowledge Base.
NV3550 Transmission Retrofit Kits
Like any transmission swap, various parts are necessary to install an NV3550 in a Jeep for which it wasn’t a factory component. For starters, you need a bellhousing and adapter plate with the correct spline counts to connect the transmission input and output shafts to your engine and transfer case. These connections have small tolerances, so using the wrong adapters can quickly cause shifting difficulties, vibrations, leaks and more.
Other parts that are often necessary for an NV3550 swap include crossmember mounts, replacement clutch slave cylinders and gear shift handles. Of course, you must also use the proper hardware like nuts, washers and pilot bushings. In certain cases, you may need to modify other parts so the NV3550 will fit.
Although DIYers can track these parts down separately, buying a professionally designed NV3550 retrofit adapter package is the easiest solution (and often the most affordable). NV3550 retrofit kits like those sold at Advance Adapters include all the high-quality parts you need for common conversions, such as Jeep CJ-7 swaps that involve the AMC 4.2L engine and stock Dana 300 transfer case. They also come with installation instructions and verify compatibility.
Switching to a Jeep NV3550 Transmission
By equipping your classic 20th-century Jeep with a more powerful 21st-century transmission, it can continue blazing a trail into the next era of off-roading. Get the right retrofit adapter package and you’ll have a smooth transition to a new transmission.