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  #1  
Old August 13th, 2017, 09:30
Desert4x4 Desert4x4 is offline
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Late model NP242 rear seal keep blowing

I bought a rebuilt NP242. Late model for a 1999 XJ.
I've replaced the rear output seal 4 times now because it keeps leaking.
Each time the inside of the seal seems to break off, as if the seal is contacting the snap ring that holds the output bearing to the shaft.
Is there supposed to be a washer behind the seal to give the seal a flat surface to ride on so that it doesnt get damaged by the snap ring?

Thanks!
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Old August 13th, 2017, 10:33
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JohnX JohnX is offline
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Re: Late model NP242 rear seal keep blowing

The seal should not be riding on any surface but the driveshaft.

Is there excessive play in the output shaft?
Driveshaft yoke worn out so it wobbles on output shaft?
Too much lift with a stock shaft so it doesn't engage the output shaft far enough?
Is the vent line for the tcase plugged?
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Old August 20th, 2017, 05:29
Desert4x4 Desert4x4 is offline
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Re: Late model NP242 rear seal keep blowing

There doesn't seem to be much if any slop in the shaft.

The yoke doesn't wobble. I do have a SYE installed.

The vent line is definitely not clogged. I can blow through it when I remove the full plug.

All I can think of is that the spring for the seal must keep falling off. Maybe that makes the seal wear out faster? So I rtv'ed the spring in place on a new seal. Next time it fails I'll try this seal with the rtv'ed spring.
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Old August 20th, 2017, 05:48
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ehall ehall is offline
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Re: Late model NP242 rear seal keep blowing

Are you lubricating the shaft before you install? The seal needs an oil film. I use some gear oil, smear onto the lip of the seal and onto the shaft before assembling.
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Old August 20th, 2017, 06:22
Desert4x4 Desert4x4 is offline
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Re: Late model NP242 rear seal keep blowing

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Originally Posted by ehall View Post
Are you lubricating the shaft before you install? The seal needs an oil film. I use some gear oil, smear onto the lip of the seal and onto the shaft before assembling.
Yeah I've been using wheel bearing grease.
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Old August 20th, 2017, 06:27
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Re: Late model NP242 rear seal keep blowing

I have had the spring fall off when driving the seal into place
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Old August 20th, 2017, 08:07
Desert4x4 Desert4x4 is offline
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Re: Late model NP242 rear seal keep blowing

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Originally Posted by ehall View Post
I have had the spring fall off when driving the seal into place
Well I just installed the seal. I used some rtv around the spring to keep it from falling off. Even when dried, the rtv doesn't seem to affect the seals flexibility .

I'll report back when it fails.
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