Nv3550 vs. Ax15: Which Is The Most Updated Transmission?

In the new millennium, Jeep customers were provided with a modern transmission in the smooth shifting NV3550. It was a contemporary take on the old Aisin AX15 transmission. Both transmissions are pretty good when it comes to power handling, although you might find that the AX15 is more convenient and more affordable.

NV3550 is commonly used in Jeep Wrangler TJs built from 2000-2004 and Cherokee XJs built from 2000-2001. As an alternative, the Japanese transmission company Aisin Warner produces the AX15 transmission, which has a 5-speed manual gearbox.

Nv3550 Vs Ax15: what’s the better transmission? Well, let’s discover.

Compare Briefly Between Nv3550 Vs Ax15

Before we get into a detailed review below, it’s necessary to review some head to head differences and similarities.

Years in usage:- 2000-20041988-1999
Length: 16.7”Length: 16.5”
Models:- XJ, TJXJ, YJ, MJ, ZJ, TJ,
Weight:- 97 lbs110 lbs
Torque capacity:- 300 lb-ft300 lb-ft
Case:- Cast aluminumWith an aluminum mid-plate and cast aluminum case
Input:- 10 Spline – 1.125″10 Spline – 1.125″
Output:- 23 Spline, Flush23 Spline, 1/2″ Out
Transmission:-  five-speedTransmission:-  five-speed
Price higher than AX15Price lower than NV3550

Nv3550 Vs Ax15: In-Depth Overview

After a brief comparison, we will now examine closely how they differ and how they are similar.


There is 16.7″ of cast aluminum in the NV3550 case, and have generous ribs. With the Jeep-I6 bellhousing attached, this measures 23.1″. There are dowel pins to ensure precise alignment to the bellhousing, as well as oval-shaped bolt patterns for the front. A throwout sleeve is integral to the front bearing retainer to accept conventional throwout bearings.

AX15 4WD transmission cases have a 16-1/2″ length. They are made of cast aluminum and have an aluminum mid plate. You will find the shifter ribbed and generously ribbed in the rear quarter of the assembly. AX15’s bellhousing alignment uses dowel pins, as in more modern transmissions.

For connecting the input shaft to the transfer case output shaft, the Jeep AX15 4WD features a 23-spline output shaft. It extends about 1/2″ beyond the transmission body.

Compatibility Of Transfer Cases

Two transfer cases were available for the Jeep 3550: the NP231 and the NP241OR. With its Jeep/ Dodge 6 bolt transfer case mount face, it can accommodate dropped transfers on the driver’s side. As it has a 23-spline driving shaft, the NP231 23 spline version is compatible.

The Jeep AX15 transfer case was factory-installed with the New Process (also called New Venture) transfer case model 231. The AX15 can be adapted to the Jeep-Dana 300 transmission by using Novak kit-153 in both the passenger and rider side drop.

Using the AX15 with a NP207 transfer case, such as those used in YJ & XJ Jeeps, requires shortening the 207’s input shaft to 2.1″ in length using a lathe or hard saw.

Vehicles Applications

A manual transmission called the NV3550 was developed by New Venture Gear for the TJ Wrangler, XJ Cherokee models of the 2000s, as well as for some Dodge pickup trucks. NV3550 was designed to replace the AX15. As opposed to the AX15- the NV3550 lasted a much shorter time before being replaced by the newer model (about 4 years).

Aisin introduced the AX15 in 1988. It appeared in several Jeep models, including the TJ and YJ Wrangler, ZJ Grand Cherokee, XJ Cherokee, and MJ Comanche as well.

Dodge Dakotas were also available with this transmission. Furthermore, it has a lot in common with the R154- transmission used on Toyota’s third generation Supra Turbo.

Years & Models

The NV3550 is designed with various updated features. This means that the input shaft has 10 splines and is 1-1/8″ in diameter. However, some Jeeps from late 2004 had input shafts with 19 splines and 1″ diameter. Approximately 23 splines make up the output shaft, and the adapter’s rear face is flush with the shaft.

For up to and including the 1993 model year, the AX15 was integrated into the slave/ throwout assembly. Until 1994, slave cylinders and cross-arms were used more conventionally. Its stick out length is 7-1/2″, and its input shaft has a spline of 10 sized at 1-1/8″.


NV3550 is a 5-speed transmission that features a direct drive gear in the 4th and an overdrive gear in the 5th. It has synchronized gears and helical gear cuts. Transmissions for 2WD and 4WD vehicles were made in different versions.

The AX15 5-speed transmission is similar to the NV3550 – it has a direct-drive 4th gear along with an overdrive 5th gear. AX15 transmissions are also fully synchronized, use helical-cut gears, and are available in both 2WD & 4WD configurations. As a long-lasting and popular transmission, the AX15 was produced from 1988 to 2000, and it is still in production today.

Ratio Of Gears

It is probably the first gear ratio that is most different between these two transmissions. The first gear ratio for the AX15 is 3.83, rather than 4.01 for the NV3550. Due to the higher gear ratio, the NV3550 is a better transmission for offroading.

NV3550 Gear Ratios:

1st= 4.01

2nd= 2.33

3rd= 1.39

4th= 1.00

5th= 0.78

R= 3.57

AX15 Gear Ratios:

1st= 3.83

2nd= 2.33

3rd= 1.44

4th= 1.00

5th= 0.79

R= 4.22

Nv3550 Vs Ax15: Which Works Best?                       

Which one is more capable between Nv3550 Vs Ax15? Due to the fact that the AX15 is an older design, the main benefit is that it is significantly less expensive than the AX3550. Another difference between the NV3550 and AX15 is the duration of production.

You’re more likely to find an AX15 in a junkyard if you’re looking for a new transmission. Regardless of which transmission you can find, both are excellent choices, so you should be happy with whatever you choose.


Which is better: AX15 or NV3550?

To summarize, the NV3550 is cheaper and simpler to acquire compared to the AX15 and is more suitable for off-roading due to its higher first gear ratio.

Are the AX15 and NV3550 interchangeable?

Jeep Nv3550s were factory-fitted with NP231- and NP241OR-transmissions. This mounting face includes the standard 6-bolt mounting pattern for Jeep/ Dodge drop-down transfer cases. This output shaft has a 23-spline, making it compatible with the NP231, which has a 23-spline—swapping AX15 for NV3550.

What Jeeps came with AX15?

Jeeps using the AX15 were equipped with an AMC-242 (4-L) Inline 6-engine, the AMC-258 (4.2 L) Inline 6-engine, and AMC (2.5 L) Straight 4-engine as well. Included in this were vehicles such as the Comanche (MJ), Cherokee (XJ), and Wrangler (TJ and YJ). Dodge Dakotas of the 2nd-generation is also available.

Last Word

Comparing these two “Nv3550 Vs Ax15” transmissions, they are pretty close. These two transmissions are quite similar with regard to their torque rating, size, gear ratio, and vehicle applications. The NV3550 is also said to shift smoother and make less noise when driving over the AX15, according to some users.

It’s not surprising, then, considering the transmission is newer. It is probably worth considering the NV3550 whenever this is important to you.

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