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The NP242 is the Selec-Trac case: the one with 2WD, Part Time, Full Time, Neutral, and 4 Lo on the lever. It sat behind the 4.0L and 5.2L in the Cherokee XJ, Grand Cherokee ZJ and WJ, and Grand Wagoneer, and a close relative shows up in Dodge trucks. What makes it different from the simpler NP231 is the center differential that lets you run 4WD on dry pavement in Full Time.
Full Time is also why 242s wear out chains. Owners leave it there all winter, so the chain carries load every mile. Past 150,000 miles, an original chain almost always has slack.
For the bigger picture on this case, including the center diff, the pump, and vacuum switch issues, see our NP242 problems and cost guide. This page is about the chain.
Symptoms of a Stretched NP242 Chain
- Clunk on and off the throttle. Lift, then get back on it, and you feel a thunk through the floor. Worse in Full Time and Part Time, often gone in 2WD.
- Slap or rattle. The slack side of the chain is hitting the inside of the case. You hear it most on decel or over bumps.
- Growl that follows road speed. Not engine speed. Hold 40 mph in two different gears and the noise stays the same.
- Glitter in the fluid. Fine metallic paste on the drain plug or in the drained fluid is chain and sprocket wear.
- Noise worse in Full Time. The center diff keeps the chain loaded through every turn and throttle change, so a loose chain is loudest there.
If you have a hole worn through the case near the chain path, you waited too long. That is a used-case job now. More in our chain stretch guide.
How to Check Chain Slack Without Opening the Case
Unbolt the front driveshaft at the front axle end and let it hang or support it. Put the transmission in Park (or in gear with the clutch out on a manual), set the parking brake, and put the transfer case in 4 Part Time. Now grab the front driveshaft and twist it back and forth by hand.
A healthy chain gives you a small amount of rotation before it goes solid. A stretched chain gives you a big, sloppy arc, and you can often hear the chain clack against the case as you reverse direction. Check the U-joints first so you are not measuring their play. Glitter in the fluid plus slop is your answer.
DIY Chain Replacement: The Procedure
This is a driveway job with a transmission jack and a helper. The case has to come straight back off the output shaft without hanging on it.
Removal
Drain the fluid. Mark and remove both driveshafts. Disconnect the shift linkage and any switch or sensor connectors. Support the case, remove the mounting nuts, and slide it back off the transmission.
Splitting the Case
On the bench, remove the rear extension or retainer and the rear output parts that hold the rear half on. Remove the case-half bolts, then use the pry slots to separate the halves. Lift the rear half straight up. The oil pump rides on the mainshaft at the rear; note how its pickup tube and screen sit before you pull anything else.
Chain and Sprockets
The chain does not come off by itself. Lift the drive sprocket off the mainshaft and the driven sprocket off the front output together, with the chain still wrapped around both. Install the new chain the same way: wrap it on both sprockets on the bench and drop them in as one assembly.
Inspect While It Is Apart
- Sprocket teeth. Hooked, pointed, or polished-thin teeth will chew up a new chain fast.
- Center differential. Look for chipped pinion teeth, worn thrust washers, and play in the carrier.
- Oil pump. Scoring on the gears or housing, and a clogged pickup screen.
- Shift fork pads. Worn thin or missing pads let the fork cut into the sleeve. Replace them every time.
- Case halves. Wear grooves where the chain has been slapping.
Reassemble with new seals and fresh sealant, torque the case bolts to the factory spec for your application, and refill before the first drive.
What Else to Replace While It Is Open
Labor is the expensive part, so do the cheap parts now. Front and rear output seals. Fork pads. Any bearing that feels rough or notchy when you spin it. And the pump if it is scored.
On the Cherokee XJ, pay attention to the rear output. The XJ uses a slip yoke that rides in a bushing at the back of the case, and when that bushing wears, the rear seal leaks no matter how many new seals you put in. If the yoke rocks up and down in the tail housing, replace the bushing along with the seal.
Fluid
Most Jeep NP242 applications call for ATF+4. Do not just take our word for it: check the tag near the fill plug and your owner's manual, since earlier years and Dodge applications may list something different. Never put gear oil in it. Fill to the bottom of the fill plug hole with the vehicle level. Our transfer case fluid guide has more on matching fluid to the case, and the tag identification guide shows where to find the model number.
NP242 Chain Job Quick Reference
| Item | Detail | Rough Cost |
|---|---|---|
| Drive chain | HV-028, 1.00 in wide, 0.500 in pitch, 36 links, round pin | $100.99 |
| Seals, sealant, fluid | Front and rear outputs, case sealant, ATF+4 (verify) | About $40-90 |
| Fork pads, bearings | Replace pads always; bearings if rough | About $40-150 |
| XJ rear bushing | If slip yoke rocks or rear seal keeps leaking | About $15-40 |
| DIY total | Chain plus reseal, or full refresh | About $150-450 |
| Shop chain job | Remove, split, chain, reseal, install | About $700-1,300 |
| Used case | Same age, likely same worn chain | About $250-600 plus install |
DIY vs Shop vs Used Case
DIY: Cheapest by far, and you know what is inside. Budget a weekend for your first one.
Shop: Make sure the quote says new chain. A reseal on a stretched chain is the same noise again.
Used case: Junkyard 242s are as old as yours. Unless you open it and chain it anyway, you are rolling dice. If you want to weigh the bigger options, our rebuild vs replace guide breaks it down.
When a Chain Alone Is Not Enough
If the sprocket teeth are hooked or worn thin, a new chain on old sprockets will be loose again sooner than you want. And if you have a chatter or bind in tight turns in Full Time that does not go away after the chain, look at the center differential: worn pinions, thrust washers, or a damaged carrier. That is a bigger rebuild, and it can tip the math toward a better used or rebuilt case. If your Jeep has the NP231 instead, the NP231 chain replacement guide is the one you want.
NP242 Chain Ships Same-Day
HV-028 drive chain for the NP242 and NP244. $100.99, same-day ship before 2pm Eastern. CoreTransmissionParts carries the broader catalog.
Shop the NP242 Chain → Shop CoreTransmissionParts →FAQ
How much does it cost to replace an NP242 chain?
Doing it yourself, plan on roughly $150 to $250 for the chain, seals, sealant, and fluid, or $250 to $450 if you add fork pads and bearings. A shop typically charges roughly $700 to $1,300 for removal, chain replacement, reseal, and installation, depending on labor rate and what else they find.
Why is my NP242 noisier in Full Time than in Part Time?
In Full Time the center differential is splitting torque between the axles, so the chain is loaded and unloaded constantly on every throttle change and in every turn. A stretched chain or a worn center differential shows up there first. If the noise goes away in 2WD and gets worse in Full Time, the chain is the first suspect.
Does the HV-028 chain fit both the NP242 and NP244?
Yes. The HV-028 is a 1.00 in wide, 0.500 in pitch, 36 link round pin chain used in the NP242 and the NP244. Confirm your case model on the ID tag before ordering, since Jeep and Dodge used several different transfer cases.
What fluid goes in an NP242 after a chain replacement?
Most Jeep NP242 applications call for ATF+4, but verify against the tag near the fill plug and your owner's manual, since earlier and Dodge applications may list a different fluid. Fill to the bottom of the fill plug hole with the vehicle level.