Cost to rebuild NP231 transfer case versus replace?

[ballpark]

1997 4.0 with AX15 and NP231
Purchased 1.5 years ago with 104K miles, currently at 114k miles.
The TC has been noisy since I purchased it. Changed fluid 2 times.
Least noisy in 2hi, more noisy in 4hi, and really noisy in 4lo.

I changed the clutch, while the TC was out, when i manually turned the shafts, I could hear the noise loud and clear. The key however, is that when the TC is in neutral, both output shafts, when rotated manually sound quiet and smooth. The input shaft is where the noise is coming from. I am pretty confident I have a noisy planetary gear.

Its a grinding noise, not a clicking noise.

I would like to rebuild it, but I am worried it would be cheaper to buy a rebuilt unit because if the planetary gear is the issue, then its $220 for the rebuild kit with chain, plus a new planetary gear set ($200) , and if the sun gear is bad, its a new housing...

Just leave it?

Any thoughts?

Thank you

 

[L0jik]

I wish I had something to help instead of just asking more questions, but if you had audio of the noise would you mind posting it? Im getting a noise from my drivetrain and im starting to wonder if its the T-Case.

 

[Chris]

I'd rebuild it personally. It's not that hard or expensive from what I've seen.

 

[EzPeezy]

If you can afford some downtime then you should pull the case apart and look at it to see what's wrong. If it's your daily driver the buy a rebuild kit and then take the case apart. The chain may have stretched and might be slapping the case somewhere.

 

[fixmysix]

Just a thought if you do replace the planetary, get the one from a 241. It has 6 gears instead of the 3 in the 231. Just be careful as the gear cut changed in 1994-95. Here's a link to a complete upgrade path for the 231. Yeah, it's Pirate, but it's a good article. I'd rebuild it but I like doing that kind of thing and it's really pretty easy.

https://www-pirate4x4-com.cdn.ampproject.org/v/s/www.pirate4x4.com/forum/jeep-non-hardcore/1503778-np231-full-upgrade-build.html?amp_js_v=a2&amp_gsa=1&amp=1&usqp=mq331AQCKAE%3D#aoh=15807625263595&referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.pirate4x4.com%2Fforum%2Fjeep-non-hardcore%2F1503778-np231-full-upgrade-build.html

 

[tworley]

I dont think the wide gear and chain is worth it. As far as I know the "upgrade" does make it stronger, but how often do you see broken chains and broken planetary gears on a completely stock 231? Id buy a rebuild kit and call it good.

 

[ballpark]

Thank you all for the info. Here is the sound with the TC outside of the jeep.

I wish I had something to help instead of just asking more questions, but if you had audio of the noise would you mind posting it? Im getting a noise from my drivetrain and im starting to wonder if its the T-Case.

Thank you! Below are two videos of the sound....

Video of TC Outside of Jeep

Video when driving

 

[ballpark]

If you can afford some downtime then you should pull the case apart and look at it to see what's wrong. If it's your daily driver the buy a rebuild kit and then take the case apart. The chain may have stretched and might be slapping the case somewhere.

Probably the best idea...

 

[ballpark]

Thank you all for the info. Here is the sound with the TC outside of the jeep.


Thank you! Below are two videos of the sound....

Video of TC Outside of Jeep

Video when driving

Any thoughts on the noise here?

 

[L0jik]

Thank you all for the info. Here is the sound with the TC outside of the jeep.


Thank you! Below are two videos of the sound....

Video of TC Outside of Jeep

Video when driving

Thanks! That actually sounds quite similar to what i'm hearing. I'll pull mine out over the weekend and see if thats where the sound is coming from.

 

[scottgraham]

Get a used one from Ebay for 200 bucks, throw that in and rebuild yours, then pull the used one out and throw it up on CL, prb break even.

 

[ballpark]

My new theory is that both of my videos are showing two different things.

1. The video with the TC outside of the jeep, is the planetary gear set, and yes it makes some noise, but its normal.

2. The video with my jeep driving down the road, its the chain, because the frequency of the noise is less than the output of the transmission. It would be a much faster click, if it was in time with the speed of the shafts. Also, 2hi would be just as loud. I think its a loose chain, that sometimes hits a frequency, or difference between the front and rear drive shaft. (also due to the common failure of chain stretch)

I am going to replace the chain, oil pump filter, seals, and plastic fork covers.... and inspect the rest...

 

[ballpark]

As a follow up. I opened up the T-Case. Ended up replacing a few seals, the input shaft bearing, and the chain. Here is the video of the bad bearing:

All my noises are gone! Backdriving in 2nd, coasting, and especially in 4hi and 4low. I did replace the chain, but I am certain it was the bearing.

Here you can see the lubrication port full of RTV: