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Unread 06-26-2013, 10:44 AM   #1
cdcutsha
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1988 YJ Wrangler 
 
Join Date: Nov 2012
Location: Austin, IN
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Strange Sound Front Axle or NP231 or Something

Hello All

I've been hearing a strange sound coming from the ole jeep and could use a little help narrowing it down. It kinda sounds like to me like a slight metal on metal sound when the 4wd is engaged.

1. All started, when the 4wd indicator light quit working and front axle would not disengage
2. checked and fiddled with vacuum lines
3. shifts out of 4wd to 2wd fine when on dirt ( front axle disengages )
4. Does not shift out of 4wd to 2wd when on the road. have to stop and put in reverse. ( sound and feels like still engaged )

so.

5. I only hear the sound when 4wd H or Low is engaged on the street. sounds like slight metal on metal
6. does not make sound in 2wd
7 So i have a shifting in and out of 4wd issue ( gonna do a permi lock )
8. Concerned with that sound

Went to 1 mechanic and they said transfer case
Went to 2nd mechanic and they said front axle bearings
Went to 3rd mechanic and they said wheel bearings in the hub



Drained and replaced fluid in front differential and transfer case ( no metal shavings )

Any help would be appreciated.

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Unread 06-26-2013, 11:48 AM   #2
squarelite
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What about the u joints on the front driveshaft?
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Unread 06-26-2013, 01:51 PM   #3
Siva283
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If the collar in the cad isnt completly engauging or disengauging it will do that. Ask me how I know. Check vacuum on both lines at the cad. It will disengauge on its own without vac but not completely.
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1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

[QUOTE=Magnum;14117863] I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim[/QUOTE]

[QUOTE=ldso;16498409]. It started with a $200 axle, and a few thousand dollars later I was done :)[/QUOTE]

[QUOTE=Luuca;16122017]diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...[/QUOTE]

[QUOTE=Overhead;17658665]this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.[/QUOTE]
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Unread 06-26-2013, 06:44 PM   #4
cdcutsha
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The U-joints were all replaced in February, all the u joints. I had a feeling that could be it siva, since i had so much problems with the vacuum lines and this all started at the same time. But why would it disengage on grass/dirt and not pavement?

All the vac lines have "vac" on them. I'm wondering if it might be either the transfer case switch or the cad motor..

I think if this is the issue, i will just perm a lock that front end.
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Unread 06-26-2013, 07:14 PM   #5
Siva283
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Quote:
Originally Posted by cdcutsha View Post
The U-joints were all replaced in February, all the u joints. I had a feeling that could be it siva, since i had so much problems with the vacuum lines and this all started at the same time. But why would it disengage on grass/dirt and not pavement?

All the vac lines have "vac" on them. I'm wondering if it might be either the transfer case switch or the cad motor..

I think if this is the issue, i will just perm a lock that front end.
The force's on it arw different on concrete. If you swerve a feq times it will probably still disengauge

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1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

[QUOTE=Magnum;14117863] I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim[/QUOTE]

[QUOTE=ldso;16498409]. It started with a $200 axle, and a few thousand dollars later I was done :)[/QUOTE]

[QUOTE=Luuca;16122017]diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...[/QUOTE]

[QUOTE=Overhead;17658665]this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.[/QUOTE]
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Unread 06-26-2013, 07:34 PM   #6
cdcutsha
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Pricing perma and posi locks, looks like i'm gonna throw one of them on.
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Unread 06-26-2013, 09:48 PM   #7
kgb_m3
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I'm willing to bet it's your transfer case chain. Mine had that as well. Could also be your u-joints. My driveshaft was solid and rear u-joints looked good during inspection. I was out of ideas after rebuilding the transfer case and still hearing the sound. Decided to do u-joints anyway, sure enough, once I pulled the caps off, there was nothing but rust inside of most. New ones in, no more sounds.
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Unread 06-26-2013, 11:10 PM   #8
Duncan542
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^^^ willing to bet that it's your chain too
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Unread 06-27-2013, 06:20 AM   #9
cdcutsha
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I will double check the U-joints this weekend, they were all supposed to have been replaced. How difficult is it to change the chain in the transfercase? If I do replace it.. Should I go with OEM or Upgrade ( if there is one, i'm assuming there is )?
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Unread 06-27-2013, 06:26 AM   #10
Duncan542
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Easy as pie, you can even do it with the t case in your jeep and yes there is a upgraded 1 1/4 thick chain instead of your stock 1 inch
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Unread 06-27-2013, 11:48 AM   #11
kgb_m3
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Quote:
Originally Posted by Duncan542 View Post
Easy as pie, you can even do it with the t case in your jeep and yes there is a upgraded 1 1/4 thick chain instead of your stock 1 inch
This.

Here's new chain installed in my np231 from Napa, ~$70



did it right on the jeep. Since you're auto, be sure to put the tranny in neutral, I had hard time putting on one of the snap on rings and couldn't figure out what was causing it to not line up.
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Unread 06-27-2013, 03:34 PM   #12
cdcutsha
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Update: Not the Ujoints.
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Unread 06-27-2013, 03:35 PM   #13
cdcutsha
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Looking into the wheel bearings, axle bearings, cad and transfercase next
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Unread 06-27-2013, 04:02 PM   #14
mike_breaker_5
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upgrading the chain is easy. you could either go through the trouble of replacing it or... go to the junk yard and find a dodge dakota with one in it from the 90's. they are clocked slightly lower but they have the HD chain in them. this is the case i am running in my rig until the d300/nv4500 swap happens.

have you ruled out the front disco yet? have you taken the cap off and looked for damaged splines at the disconnect? it's alot easier to check that and rule it out than to crack the x-case, change the chain, and only to still have the noise. usually in my experience at least... x-case problems will transfer vibs through the trans and feel like the problem is there... not the front axle.

may also be a R&P or carrier issue in the front. dirt lets the grippy tire slip easier, pavement does not. if there's something catching in your spiders or anywhere in the diff for that matter, it would be more prevalant while on a grippy surface in 4wd. whatever it is it sounds like it's axle related to me. remember the yj is a different bird when it comes to the front axle. your front DS does not have to spin when you are driving in 2wd like most other 4wd vehicles with open diffs. with the x-case in 2wd and the cad disconnected you have one tire spinning one way and the long shaft is free to spin separate of the hub.

i am going to go against the crowd and say it's in the front axle.
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Unread 06-27-2013, 04:55 PM   #15
Damon1995
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i have a suspicious grinding that i can hear when i let off the gas. i know it something in the np231 because i changed the fluid and it went away. then it came back the next time i shifted into 4wd and even when i put it back in 2wd it still grinds. but i dont really give a **** because i have a spare 231 in the garage
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