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Every JK transfer case output has a yoke or flange splined onto the shaft, and the output seal rides directly on the neck of that yoke. That is why a yoke gets replaced far more often than people expect. Once the seal surface is grooved, pitted or rusted, a brand-new seal leaks within weeks, and the owner blames the seal. The fix is the yoke.
JKs are also hard on yokes for a second reason: lifts. A two or three inch lift steepens the driveshaft angles, the joints work harder, and any looseness in the yoke splines turns into clunk and vibration.
Signs the Yoke Is the Problem
| Symptom | Likely Cause | What to Check |
|---|---|---|
| Output leak returns after a new seal | Grooved or pitted seal surface on the yoke neck | Run a fingernail around the neck; any catch means replace it |
| Clunk shifting Drive to Reverse or engaging 4WD | Worn yoke or output splines, loose output nut | Grab the yoke and twist; there should be no rotational play on the splines |
| Vibration that builds with speed after a lift | Driveshaft angle, bent yoke ear, worn U-joint | Measure driveshaft and pinion angles; inspect yoke ears and joint caps |
| Low fluid, chain noise in 4WD | Long-term leak at the output | Check fluid level at the fill plug before anything else |
Do not ignore a slow output leak. The NV241 holds a small amount of fluid, and a case that runs low takes out the chain, the pump and the bushings. If a leak is what you are chasing, our output shaft seal replacement guide covers the seal side of the job.
1310 Yoke vs 1350 CV Flange
Stock-style 1310 end yoke
For a stock or mildly lifted JK keeping a conventional driveshaft, a direct replacement yoke is the fix. Our JK NP241 end yoke (TEN Factory MG13443) is a 32-spline, 1310 series yoke that fits the front or rear output of the JK case and replaces JE Reel 2-4-JK03 and Neapco N2-4-JK03.
1350 CV flange
Bigger lifts push the rear driveshaft angle past what a single U-joint handles smoothly. The usual answer is a double cardan (CV) driveshaft, which bolts to a flange instead of a yoke. The Yukon NV241 1350 CV rear output flange is built for JKs running an aftermarket NP241 swap with a 1350 CV rear shaft. It is not a direct replacement for the factory output, so check spline count, seal size and bolt pattern against your case and driveshaft first.
Rule of thumb: if you are replacing a worn part on a near-stock Jeep, match what came off. If you are fixing lift vibration, sort out the driveshaft and angles first, then buy the yoke or flange that matches the shaft.
Replacement Steps
- Chock the wheels, put the transmission in Park and the transfer case in 2H.
- Paint-mark the driveshaft and yoke so the shaft goes back in the same phase.
- Remove the U-joint straps or flange bolts and hang the driveshaft out of the way. Tape the U-joint caps so they do not fall off.
- Hold the yoke with a holding tool and remove the output nut. Pull the yoke straight off with a puller; do not hammer on it.
- Replace the output seal while the yoke is off. It is a few dollars and the seal is already exposed.
- Lube the new seal lip and the yoke neck, slide the yoke on, and install a new output nut torqued to the factory spec in the service manual.
- Reinstall the driveshaft on its marks, torque the straps, then top off the transfer case fluid. Jeep specifies ATF+4 for the JK NV241; confirm in your owner's manual.
Fix the Leak the Right Way
Direct-fit JK yokes and CV flanges for the NV241 family. Free shipping on every order.
Shop JK 1310 Yoke → 1350 CV Flange Core Transmission PartsFAQ
Why does my JK transfer case keep leaking after I replaced the output seal?
The seal rides on the neck of the output yoke. If that surface is grooved, pitted or rusted, a new seal cannot seal against it. Replace the yoke along with the seal.
Does the same yoke fit the front and rear output on a JK?
The TEN Factory MG13443 32-spline 1310 yoke fits either the front or rear output of the JK NP241 case. Always confirm spline count and U-joint series on your own case and driveshaft before ordering.
Do I need a CV flange after lifting my JK?
Not always. Small lifts often run fine on the stock-style shaft. If a bigger lift causes vibration that builds with speed, a double cardan (CV) driveshaft on a matching flange is the usual fix. Sort out the driveshaft first, then pick the yoke or flange that matches it.
Can I reuse the transfer case output nut?
It is better not to. Install a new output nut and torque it to the factory spec in the service manual so the yoke stays tight on the splines.
What fluid goes in a JK transfer case?
Jeep specifies ATF+4 for the JK NV241 Command-Trac and Rock-Trac cases. Check your owner's manual, then fill until fluid just starts to run out of the fill plug hole.