NP231 output bearing noise

[4x4AZ]

Hi, all. New here after acquiring a 2000 TJ 4.0 nv3550 5 speed from my wife's family. It's had some work done to it over the years including a SYE kit, a 4" (I believe) lift, a Ford 8.8 rear axle swap w/ a truss, and 4.56 gears.

This thing is a bit of a mess, mechanically. It's had a very noticeable "rumble" in 5th and a very harsh "banging" engagement into gear since I got it, and it's also got a "clicking" sound that I notice under normal low speed acceleration that seems to be either from the transfer case or the transmission area. It also has a cyclical very deep hum at highway speeds that I'm thinking is from the rear end, but that's a separate topic

So far, I've replaced all control arms and the U-joints on the rear driveline. Track bar bolts are new as well.

Today I pulled the driveshaft to try to replicate some of the sounds I have been hearing and noticed the following. To me this sounds indicative of a bad bearing, would you guys agree? If so, what should be my next steps? Should I rebuild the whole case, do I need a new SYE kit, or is this just likely a single bearing that wouldn't be that hard to fix? Please excuse my lack of familiarity with SYE setups, I've never owned a jeep before so they are new to me Thank you!

 

[JMT]

Hi, all. New here after acquiring a 2000 TJ 4.0 nv3550 5 speed from my wife's family. It's had some work done to it over the years including a SYE kit, a 4" (I believe) lift, a Ford 8.8 rear axle swap w/ a truss, and 4.56 gears.

This thing is a bit of a mess, mechanically. It's had a very noticeable "rumble" in 5th and a very harsh "banging" engagement into gear since I got it, and it's also got a "clicking" sound that I notice under normal low speed acceleration that seems to be either from the transfer case or the transmission area. It also has a cyclical very deep hum at highway speeds that I'm thinking is from the rear end, but that's a separate topic

So far, I've replaced all control arms and the U-joints on the rear driveline. Track bar bolts are new as well.

Today I pulled the driveshaft to try to replicate some of the sounds I have been hearing and noticed the following. To me this sounds indicative of a bad bearing, would you guys agree? If so, what should be my next steps? Should I rebuild the whole case, do I need a new SYE kit, or is this just likely a single bearing that wouldn't be that hard to fix? Please excuse my lack of familiarity with SYE setups, I've never owned a jeep before so they are new to me Thank you!

Well, it doesn’t sound good and it sounds like it’s coming from that area as you move the phone around, but hard to tell.

The case probably has 150k miles on it. It would be a good idea to rebuild it. Parts kits are about $165. The bearing comes with it. Your SYE is probably ok.

 

[CharlesHS]

IF you decide to rebuild the transfercase; ensure the kit comes with a replacement chain.

 

[AaronPaul]

Hi, all. New here after acquiring a 2000 TJ 4.0 nv3550 5 speed from my wife's family. It's had some work done to it over the years including a SYE kit, a 4" (I believe) lift, a Ford 8.8 rear axle swap w/ a truss, and 4.56 gears.

This thing is a bit of a mess, mechanically. It's had a very noticeable "rumble" in 5th and a very harsh "banging" engagement into gear since I got it, and it's also got a "clicking" sound that I notice under normal low speed acceleration that seems to be either from the transfer case or the transmission area. It also has a cyclical very deep hum at highway speeds that I'm thinking is from the rear end, but that's a separate topic

So far, I've replaced all control arms and the U-joints on the rear driveline. Track bar bolts are new as well.

Today I pulled the driveshaft to try to replicate some of the sounds I have been hearing and noticed the following. To me this sounds indicative of a bad bearing, would you guys agree? If so, what should be my next steps? Should I rebuild the whole case, do I need a new SYE kit, or is this just likely a single bearing that wouldn't be that hard to fix? Please excuse my lack of familiarity with SYE setups, I've never owned a jeep before so they are new to me Thank you!

The NV3550 is a sturdy transmission, but if the bearings inside have started to wear, they could cause noise or difficulty engaging gears. The rumble could be from bearings inside the transmission that are starting to fail, especially if it's more noticeable in 5th gear.

This hum at highway speeds could be indicative of a few things, particularly the rear axle. Given that the vehicle has had a rear axle swap, it's possible that the noise is coming from the differential or the gearing. The 4.56 gears in the Ford 8.8 rear axle could be causing this noise if they're not properly set up, or the bearings in the axle could be worn.

There are a lot of smart guys on here. What have you figured out so far?