AX-15 to NV3550 Swap

Difficulty 4/512–30 hrs$600–15001989-1990, 1991-1995, 1996, 1997-2001

Direct swap into 89-99 XJs that already had AX-15. Bolt pattern, input shaft, output spline all line up. Pulls stronger 5-speed with same ratios.

The NV3550 (built by New Venture Gear) succeeded the AX-15 in 2000-2001 XJs and continued in TJs through 2004. Same ratios as the AX-15 but heavier-duty internals — Aisin gear quality with NV designs.

The swap from AX-15 to NV3550 is one of the cleanest in the XJ world:

Same bolt pattern to the 4.0L bell housing
Same input shaft length and spline (10-spline, 1-1/8")
Same output flange to NP231 transfer case
Same crossmember
Same shifter location

What's different:

NV3550 has a slightly different shifter offset, may need different boot
Bell housing is integrated on NV3550 (on AX-15 it's separate). When swapping AX-15 to NV3550 you use the NV3550's integrated bell.
Clutch hydraulic line angle changes slightly
TJ-sourced NV3550 may need a Cherokee tail housing if t-case alignment is off

Why do it: NV3550 handles 4.6 stroker torque better than AX-15 (less 1-2 fork bend, stronger synchros). Common in donor TJs at junkyards.

Donor options: 2000-04 TJ Wrangler with 4.0L, or 2000-01 XJ. ~$300-700 at a pull-a-part. Add new clutch (Centerforce or Luk), pilot bearing, throwout bearing, hardware.

Why it works

bolt-in upgrade
stronger trans
same ratios

Trade-offs

donor sourcing
labor

Tools required

transmission jack
engine support bar
socket set
clutch alignment tool

Parts

Part	Vendor	Est. price
NV3550 trans (junkyard)	junkyard	~$500
Centerforce II clutch kit	Centerforce	~$280
Pilot bearing	Mopar	~$15

Sources

{'title': 'NV3550 swap thread', 'url': 'https://www.cherokeeforum.com/f2/nv3550-swap/'}

Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.