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Unread 01-20-2010, 07:38 PM   #1
bigred94
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helpp np231 problems

i have the np 231 in a 94 yj 4.0 with the ax15 running 35s with 410s. when i take off i have realy bad vibs in the jeep, i was runing no rear dshaft and had the same vibs and its getting bad. wen i accerate hard right and 3500rpm it feels like the drive shaft is bidding but its not i cheaked it all out. only happens 1st and 2nd gear ive never blown up a tcase before so im unsure wat symptems they have before blowing. and the chain is realy loud realy loud on highway driving has fuild in it. anyone have any ideas??


Last edited by bigred94; 01-20-2010 at 08:05 PM..
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Unread 01-20-2010, 07:46 PM   #2
msprooch
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Not trying to be a **** but using complete sentences and punctuations would help us help you.
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Unread 01-20-2010, 08:02 PM   #3
bigred94
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ok well sorry next time i will
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Unread 01-20-2010, 08:07 PM   #4
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Remember the ft driveshaft is not balanced . Check your u-joints .
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Unread 01-20-2010, 08:08 PM   #5
bigred94
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true but it shouldnt be the same vib as the rear
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Unread 01-20-2010, 08:09 PM   #6
kloppk
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You ought to check the tranny mount. Over time they will start to tear and seperate allowing the tranny to shift around under high torque loads.
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Unread 01-20-2010, 08:12 PM   #7
bigred94
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brand new poly tranny mount but that woundnt give me bangin noises under the jeep under hard acceration
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Unread 01-20-2010, 08:53 PM   #8
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Your profile says that you have a 2.5L, but it looks like you did a 4.0L swap. Is that right?

What model Jeep did the AX-15 come out of?

If it's an XJ AX-15, then your T-case might be hitting the skid. XJs have the T-case angled down 10 degrees on the drivers side & will interfere with the skid on a YJ.

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No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

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Unread 01-20-2010, 09:07 PM   #9
bigred94
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yea did the 4.0 swap in november and had no problem until 3 weeks ago .. pulled out an zj in the woods and now i have the vibs and banging.. and as for the ax15 its yj but the jeep i took it out off it had a cut cross member in it. and i have a transercase drop in the jeep now maybe i should change out the tcase and cut the cross member .and hope for the best. the chain is crazy loud in it also
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Unread 01-20-2010, 09:16 PM   #10
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Originally Posted by bigred94 View Post
yea did the 4.0 swap in november and had no problem until 3 weeks ago .. pulled out an zj in the woods and now i have the vibs and banging.. and as for the ax15 its yj but the jeep i took it out off it had a cut cross member in it. and i have a transercase drop in the jeep now maybe i should change out the tcase and cut the cross member .and hope for the best. the chain is crazy loud in it also
It sounds like a XJ AX-15 was put in the YJ you got it from.

When using a non YJ AX-15 in a YJ, the NP231 transfer case will hit the skid plate because the T-case is "clocked" 10 degrees lower on the driver side, but you can redrill the location of the mounting holes at the rear of the AX-15.

This pic & explanation were stolen by me from fellow JF member "idaholtby", he posted this in another thread a while back.

The transfer case clocking is determined by the mounting holes on the output of the transmission. Simply redrill the holes to raise the transfer case to the YJ height. In this pic, the holes on the right on each tab are the newly drilled holes that the YJ configuration requires to clear the skid plate.


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Unread 01-20-2010, 09:17 PM   #11
93jeepyj
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Maybe what your hearing is bearings that are shot in that t case, That will cause vibration on the highway Ive had it happen. Im also pretty sure the chain doesnt move in a 231 unless you're in 4wd so thats probably not the noise you're hearing. Has the t case even been run low or dry on fluid?
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Unread 01-20-2010, 09:22 PM   #12
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My jeep was making a terrible banging noise and it was the chain in the T-case. They get worn and stretched out and make all kinds of neat sounds... I've destroyed two NP 231's... When I find a good deal on one I buy it and try to keep a spare on hand.
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Unread 01-20-2010, 09:26 PM   #13
bigred94
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yea probaly is an xj ax15 but the tcase is deff an yj and my front shaft aways moves if i put it in 4hi on the road i get no noise its not there anymore but the vibs are only there 1st and 2nd from dead stop and hard accleration is crazy it feels like the drive shaft is hitting the ujoints but its not theres no marks on it i have a spare tcase outa 4.2 auto yj im gonna switch see if it helps
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Unread 01-20-2010, 09:41 PM   #14
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With the jeep in neutral grab drive shaft and spin it back and forth and listen for the chain to slap around in there... I could hear mine smacking the case when I did this.
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Unread 01-20-2010, 09:43 PM   #15
Mean Max
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Quote:
Originally Posted by bigred94 View Post
yea probaly is an xj ax15 but the tcase is deff an yj and my front shaft aways moves if i put it in 4hi on the road i get no noise its not there anymore but the vibs are only there 1st and 2nd from dead stop and hard accleration is crazy it feels like the drive shaft is hitting the ujoints but its not theres no marks on it i have a spare tcase outa 4.2 auto yj im gonna switch see if it helps
The origin of the T-case (XJ or YJ) makes no difference with respect to "clocking".

The difference is only in the AX-15's T-case mounting hole pattern.

If the T-case is touching anywhere (like on the skid) you will feel driveline vibs. While in lower gears (like 1st & 2nd) and under hard acceleration, the most torque is being applied to the driveline. Again, if there is contact (or really close tolerances) between the T-case & skid (or any other portion of the frame) you can expect knocking noises & vibes.

Pics of the T-case to skid clearance would be helpful.

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There is no situation that cannot be improved with a small but well-placed explosive.
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