NP231 Problems

Wanted to throw this out for some of you more experienced troubleshooters. My son woke me up yesterday and said his 99 TJ was making a noise underneath the Jeep. Went for a very short test drive and the noise is metal sounding as you drive. Got underneath to check U joints and all appear in good shape. From the sound it was making and doing some research on the internet, pretty much sounds like Transfer case problems. We did change the fluid about 5 months ago with chrysler atf+4. My question , is this maybe a chain with slack hitting the bottom of the case or are we looking into major stuff here. Wondering if we caught this early enough to lessen the damage before the entire thing explodes. Jeep is on house arrest untill repairs can be done. Just wanting some feedback. Thanks.....

Start by disconnecting the front driveshaft. Drive it without it. If sound still there, put it back and now take the rear driveshaft out. Drive it in 4x4. Hopefully is just the u-joint.

If not, working on the NP231 is easy. I just installed a teralow and sye on mine. No special tools needed. It might just be one of the bearings and if I remember right you can replace them (two) without taking everything apart.

Could be a very slack chain.

You can also just drain the fluid and see how much metal comes out.

Pinpointing noises from underneath the Jeep can be deceptive. Work methodically and you'll find it.

So i got to check it out today. Drained the fluid and found no metal in it which im pretty sure is a good thing. I will be tearing the transfer case out in the next couple of days. Im pretty confident that its just a chain with some slack in it. Will find out soon. Thanks for the input guys. Gotts wait untill i get a few days off to really get into it.

I'd check the drive shafts and ring and pinion next before pulling the transfer case apart. Just .02

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X2