Help!! NP231 Problems - Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today

Thread Tools Search this Thread

Please support our sponsors and let them know you heard about them on
Old 01-03-2014, 08:40 PM
Thread Starter
Join Date: Jan 2014
Location: Harrisonburg, VA
Posts: 1
TJefferson98 is on a distinguished road
Help!! NP231 Problems

Hi guys, I've got a rather long post ahead of me here. I've got a 1998 TJ that was purchased new by my brother in 98. It came with a 2.5, AX-5, and an NP231. The 2.5 threw a rod, so my brother swapped in a 4.0 and an NVG3550, retaining the factory NP231. The wife came, and the Jeep got old. The Jeep sat for approximately 2 1/2 years before I bought it from him. It was stock on 31's. I wheeled it, and occasionally heard a pop, it seemed to happen during articulation so I assumed it was a spring. This would ONLY happen OFF-ROAD in 2WD. I put 2.5" springs with .75" spacers on the Jeep, and also put on 1.25" Transfer case pucks to correct driveshaft angles. A few weeks later I heard the pop happen more frequently off road so I decided to replace the rear DS U-Joints. Ended up finding out my spider gears were about to grenade while checking the rear end, so I replaced it with a quality gear set. I backed the Jeep out of the shop, and the clunk happened again. So, I decided to replace the front DS U-Joints. I did drive it without the front drive shaft and the clunk remained. One thing I should note is that my linkage needs adjusted, because it really doesn't want to go into 4-HI but will function in 4-LO occasionally popping out. Fast forward, the clunk is happening every time I let out on the clutch, as soon as it hits the friction point allowing the front driveshaft to turn. (Still in 2WD) The front drive shaft appeared as if it were binding, so I chased it down the line and noticed that the needle bearings in the front axle U-Joints were non-existent. So, after having to red wrench the U-Joints out, I replaced them with Dana/Spicer. We are now at present day, after the U-Joints were installed it seemed to quiet the popping from driving forward, but sounds AWFUL when releasing the clutch to go in reverse. Under no circumstances will it pop in 4 Wheel Drive. I can drive it, and it will pop when starting and will sometimes continue to pop while going through gears up to 4th. I have checked the transmission mount, and it is not cracked.
Thanks in advance, sorry for the long post. Just trying to provide as much information as possible to help decipher. Before you ask, I have used the search function on numerous forums, and have been researching this constantly for a month with no success. I have found similar problems, where others had a loose chain causing 4WD popping. I have also considered that possibly the T-Case is in 4WD and the chain is loose, but the Jeep does fine as far as turning and on road handling. My brother says that he has never had any problems. *Note: All fluids were changed when I bought the Jeep from my brother in June.
TJefferson98 is offline   Quote
Old 01-04-2014, 03:44 PM   #2
jlgtx's Avatar
Join Date: Dec 2013
Location: Texas
Posts: 31
jlgtx is on a distinguished road
It sounds to me like there's a problem in the transfer case. Pain in the rear, I know, but I'd open it up and check it out.

The unfortunate off-roader's prayer...Psalm 69:1-15
jlgtx is offline   Quote
Old 01-04-2014, 03:49 PM   #3
Knows a couple things...

WF Supporting Member
Jerry Bransford's Avatar
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 42,396
Jerry Bransford is on a distinguished road
There is a difference between 231's input shaft made for the 2.5L vs. the 4.0L transmissions, can I assume the 231 had its input shaft changed since you say it has the same 231 now as when your TJ had the 2.5L engine? Assuming that was done, was the chain inside the 231 checked for wear/stretch at that time?
When you have a choice, buy American.
Jerry Bransford is online now   Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 11:36 PM.

User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC. is not in any way associated with the Chrysler Motors LLC
« Back

Enter your email address:

Delivered by FeedBurner