AX-15 to NV3550 Swap
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
Related
Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.