Aisin-Warner AX15

The Aisin-Warner AX15 Transmission was a standard shift 5 speed transmission used in Jeeps between 1988 and 1999. It is a medium-duty transmission that is found behind the AMC 4.2L I6 and AMC 4.0L I6 engines. It is well known that this transmission can handle even more power than the stock 4.0L, with many running the AX15 behind LS swaps and stroker inline-6’s.

There were two main types of AX15s – those between 1988-1993 and those manufactured after 1994. Before 1994, the slave cylinder was internal which required the opening-up of the transmission to repair the slave cylinder and any leaks it may have. In 1994, AX15s were upgraded and fitted with an external slave cylinder that can be replaced within a matter of minutes with the transmission still in the vehicle. If you are in the market for an AX15, I would search for one made in 1994 or later.

Need help changing the fluid or performing other repairs? Jump to the write-ups section below.

The AX15 transmission is sensitive to GL lube that contains sulfur. Sulfur reacts with the brass parts in the transmission leading to premature failure. Mopar recommends 75W-90 API Grade GL-3 gear lubricant. GL-3 lubricant is discontinued, and can very rarely be found for purchase. Fortunately, these transmissions have been approved to run on Synthetic 10W-30 Motor Oil. Others recommend Redline MT90 as another safe option.

The correct level can be set by simply filling to the bottom edge of the fill plug hole.

More information about the AX15 can be found here.

Gear Ratios

Reverse4.22
1st Gear3.83
2nd Gear2.33
3rd Gear1.44
4th Gear1.00
5th Gear0.79

Fluid Type and Capacity

Lubricant75W-90 GL-3 or GL-4
Capacity (2WD)3.32 qts (3.15L)
Capacity (4WD)3.27 qts (3.10L)
Avoid GL-5 lubricant, which can cause increased wear on the brass synchros found in this transmission

Other Specifications

Weight94lbs
Length (2WD)16.75″
Length (4WD)16.5″
Input Splines10
Output Splines23
Pilot Tip Diameter1989-91: 19/32″
1992-99: 3/4″

Transfer Case Compatibility

The AX15 was attached to the New Process Model 231 transfer case.

You can adapt the Jeep Dana 30 transfer case using a kit by Novak found here.

It is also possible to adapt the New Process Model 207 transfer case to this transmission, but you will need to shorten the input shaft of the transfer case to 2.1″ of stick-out length to prevent bottoming out.

Engine/Bellhousing Compatibility

As is, the AX15 is compatible with the AMC 4.2L I6 and AMC 4.0L I6. It may be adapted to Ford, GM, and other AMC engines with adapters.

Write-ups and Tutorials

AX15 Full Rebuild

The Jeep Repair currently doesn’t have their own write-up on rebuilding an AX15, but will soon! In the meantime, YouTuber “UCanDoIt2” does a video series on rebuilding his AX15. Find the first video here

AX15 Fluid Change

AX15 Shifter Bushing Replacement

Parts and Fluids

Engine Fluids

EngineFluid TypeCapacity
AMC 2.5L I4Above 0°F: 10W-30
Below 60°F: 5W-30
4.0 qts
AMC 4.0L I6Above 0°F: 10W-30
Below 32°F: 5W-30
6.0 qts
GM 2.5L I4Above 0°F: 10W-30
Below 0°F: 5W-30
3.0 qts
Renault 2.1Ltbdtbd
VM Motori 2.5Ltbdtbd

Transmission Fluids

TransmissionFluid TypeCapacity
Chrysler A904 3-Speed
Aisin-Warner AW-4 4-Speed
Chrysler 30RH 3-Speed
Borg-Warner T-4 4-Speed ATF Dexron II1.75qts
Aisin-Warner AX4 4-Speed75W-90 GL3 or GL4
10W-30 Motor Oil
2WD: 3.7qts
4WD: 3.5qts
Borg-Warner T-5 5-SpeedATF Dexron II1.75qts
Aisin-Warner AX5 5-Speed75W-90 GL3 or GL4
10W-30 Motor Oil
2WD: 3.7qts
4WD: 3.5qts
Peugeot BA-10/5 5-Speed
Aisin-Warner AX15 5-Speed75W-90 GL3 or GL4
10W-30 Motor Oil
2WD: 3.32qts
4WD: 3.27qts
New Venture Gear NV3550 5-SpeedMopar MT Fluid
SAE 30W Oil
3.3qts

Axle Fluids

AxleFluid TypeCapacity
Dana 3075W-90
75W-140 (towing)
1.26qts
Dana 3575W-90
75W-140 (towing)
1.75qts
Dana 4475W-90
75W-140 (towing)
2.00qts
Chrysler 8.2575W-90
75W-140 (towing)
2.11qts

Transfer Case Fluids

Transfer CaseFluid TypeCapacity
NP207
NP228/229
NP231
NP242

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4.0L

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