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  #1  
Old November 15th, 2018, 15:23
XJ_NorCal XJ_NorCal is offline
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Leaking NP 231 - recommended seal kits?

My Transfer Case has been leaking ever since I installed my Rough Trail SYE kit by Crown. My TC skidplate is covered in oil. My winter off-season is here so it's time to fix the leak. I was planning on removing my TC and replacing all the seals rather than try to chase down a leak. Can somebody point me to a good seal kit.

Also, when I installed the SYE I noticed there was no gasket between the transmission and Transfer case mating surfaces. Does that sound right?


1998 Jeep Cherokee Sport
116K miles
4.0 litre
AW4
NP231 Transfer Case
D30 Open
C8.25 Trac-lok LSD
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  #2  
Old November 16th, 2018, 05:15
RCP Phx RCP Phx is online now
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Re: Leaking NP 231 - recommended seal kits?

There's only 3 seals, so a "kit" isn't needed but I prefer Timken for the brand. Do you even know where it's leaking from? My seals were all good but it was leaking from the tail-cone and case halves.
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Old November 16th, 2018, 07:16
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Anak Anak is offline
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Re: Leaking NP 231 - recommended seal kits?

I would call John at JB Conversions and ask him for whichever seals he has that are likely to fit. He may not have a rear output seal for you because his design may differ from Crown's design. You might need to have an O.D. measurement off your existing seal in order for him to determine if his will fit or not.

JB Conversions uses the best seals I have been able to find. It is a double lip, double spring design. For a brief time this was a production style of seal, but the bean counters got to it. John tracked down the manufacturer and has gotten them to make these seals for him. I know of no other source.

WRT the gasket between the T-case and transmission, I am one who believes it should be there. You will find plenty of others who say it doesn't matter. It is not an easy gasket to find. What I have been told is that it comes with a transmission rebuild kit. I have managed to find them however. Border Parts in Spring Valley, CA has them. They don't have a part number for them though (I asked). It is just one of the many gaskets they have hanging on the wall behind the counter. I was able to take the remnant of my old one and match it up. Getting one over the phone might be a bit tricky, but those guys know their stuff pretty well and they probably have an NP231 kicking around and could probably match a gasket to it.
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Old November 16th, 2018, 07:39
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ehall ehall is offline
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Re: Leaking NP 231 - recommended seal kits?

I just buy the individual Timkens

The paper gasket between the trans and tcase is only there to keep water and dirt from getting between them, not for keeping fluids in
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Old November 16th, 2018, 08:25
XJ_NorCal XJ_NorCal is offline
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Re: Leaking NP 231 - recommended seal kits?

Quote:
Originally Posted by RCP Phx View Post
There's only 3 seals, so a "kit" isn't needed but I prefer Timken for the brand. Do you even know where it's leaking from? My seals were all good but it was leaking from the tail-cone and case halves.
I have no idea where it's leaking from. There's oil kinda everywhere but particularly the seal on the tail cone and also near the speedometer gear. I plan on removing the TC, opening it up to reapply RTV between the 2 halves and replace all the seals since I'm not sure where it's leaking from.
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Old November 19th, 2018, 20:40
cody4359 cody4359 is offline
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Leaking NP 231 - recommended seal kits?

The speedo gear o-ring was the major culprit on mine. Got mine from quadratec. Before wasting time unless your bored, why not clean every hi g off and go for a spin then inspect where it's leaking.

I have a spare tranny and tcase that I just seperated, no gasket or sealant between the two, nice and clean.

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Old November 26th, 2018, 14:11
XJ_NorCal XJ_NorCal is offline
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Re: Leaking NP 231 - recommended seal kits?

Quote:
Originally Posted by cody4359 View Post
The speedo gear o-ring was the major culprit on mine. Got mine from quadratec. Before wasting time unless your bored, why not clean every hi g off and go for a spin then inspect where it's leaking.

I have a spare tranny and tcase that I just seperated, no gasket or sealant between the two, nice and clean.

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You know, you make a great point lol. I ordered the speedo gear o-ring. Here's to hoping it's that easy!
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Old December 1st, 2018, 10:06
md21722 md21722 is offline
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Re: Leaking NP 231 - recommended seal kits?

Quote:
Originally Posted by XJ_NorCal View Post
You know, you make a great point lol. I ordered the speedo gear o-ring. Here's to hoping it's that easy!
I bought a Crown speedo gear o-ring and it never sealed properly. I ended up getting one at the dealer. 6035709 is the part number. They had a bunch in stock at $7.20/ea. It works perfectly as is visibly thicker than the Crown.
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  #9  
Old December 5th, 2018, 09:16
XJ_NorCal XJ_NorCal is offline
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Re: Leaking NP 231 - recommended seal kits?

The speedo gear o-ring was not the culprit. I'm not sure where the leak is coming from. Any other known leak points on an NP231 transfer case that I should/could investigate with out dropping the TC?
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  #10  
Old December 5th, 2018, 10:27
RCP Phx RCP Phx is online now
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Re: Leaking NP 231 - recommended seal kits?

The selector shaft seal and detent plug, other than using a good sealer......
See #14 https://naxja.org/forum/showthread.php?t=1150862
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  #11  
Old December 5th, 2018, 16:58
XJ_NorCal XJ_NorCal is offline
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Re: Leaking NP 231 - recommended seal kits?

Quote:
Originally Posted by RCP Phx View Post
The selector shaft seal and detent plug, other than using a good sealer......
See #14 https://naxja.org/forum/showthread.php?t=1150862
Detent plug? I know you're not referring to the drain plugs but I don't recall there being any other plugs. The exploded assembly below shows a detent plug but doesn't clearly indicate its assembled location.

Also, is the "selector shaft" part of the shift linkage? Could you please use the attached exploded assembly to specify the parts you're referring to or upload a photo. I'm a little confused if you can't tell. thanks!

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Old December 5th, 2018, 19:30
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Anak Anak is offline
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Re: Leaking NP 231 - recommended seal kits?

#46 is your selector shaft seal and #2 is your detent plug.

The selector shaft is the rod of your shift linkage going into the side of the case on the driver's side.

The detent plug is really nothing more than a spring loaded ball that pushes against a notched cam on the shift linkage so as to give you a feel for when you have reached your selected gear. It is not a drain plug. Your drain and fill plugs are both on the same face of the back side of the T-case (#33 & #34 on the diagram). It would be rather unlikely the detent plug is leaking. There are no moving parts associated with its seal. And certainly don't pull it without considering the presence of the spring loaded ball and making sure you are prepared to keep track of the ball and the spring.

Note that you also have a vent tube on top of the case. Make sure that is properly connected to the vent line. I don't think that could create much of a leak, but it is worth checking. (That would be item #6 in the diagram)

Note that item #5 is a switch which also has a seal.

Other than that you have the two output seals, the joint between the tail-cone and the rear case half and the joint between the two case halves.

If it is hard to find the leak it might be worth finding a way to clean up the case. Perhaps a trip to a car wash with a degreaser.
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  #13  
Old December 23rd, 2018, 09:44
cody4359 cody4359 is offline
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Leaking NP 231 - recommended seal kits?

Fixed yet?

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  #14  
Old December 26th, 2018, 08:01
XJ_NorCal XJ_NorCal is offline
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Re: Leaking NP 231 - recommended seal kits?

Quote:
Originally Posted by cody4359 View Post
Fixed yet?

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I put in a new Speedometer gear O-ring but that didn't fix the leak. I ran into another problem and simply haven't had the time to keep looking for the leak during the holidays. I'll keep this thread updated though as I'll have more time in Jan.
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Old December 27th, 2018, 04:31
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ehall ehall is offline
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Re: Leaking NP 231 - recommended seal kits?

if you get a minute, spray the whole thing with gunk engine cleaner and hose it off after a few minutes, will make it easier to find the leak
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