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NP231 from TJ into YJ?

I'm replacing a dead NP231J transfer case in my '92 YJ (4.0L, 5 speed). There seem to be a large number of used, low-mileage TJ-version NP231's around, which leads me to the following questions regarding interchanging between the YJ and TJ versions:

  1. Other than the fluid-retension setup, are there any differences between these two versions that would be issues in using a TJ version on a YJ?
  2. Barring major incompatabilities above, what adaptations need to happen to use a TJ case on a YJ?
  3. Are there issues with a TJ case, SYE kit and CV driveshaft in a YJ?

I've got the old transfer case out, so I'd appreciate the group's opinions on this setup, particularly from anyone who has done it.

Thanks! Dave

Reply to
Mighty Monad
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I don't think there will be any functional differences.

Possibly shifter-lever opening trimming, unless you are able to use the existing YJ shift lever, which I am pretty sure you can.

Driveshaft length...you'd probably install the case to measure for the new driveshaft, and pinion angle..you'd have to install wedge inserts to correct the pinion angle for the new driveshaft.

  • * * Matt Macchiarolo
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Reply to
Matt Macchiarolo

Reply to
L.W.(ßill)

Only potential issue I can see - besides the new driveshaft - would be the spline count on the input shaft to the tc. I think it's the same but it could differ between auto/manual versions.

Reply to
Will Honea

DOH! Forgot about that damn vacuum disconnect! My advice...remove it and either install a cable-actuated disconnect or a solid axleshaft, like Real Jeeps use :-)

  • * * Matt Macchiarolo
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Reply to
Matt Macchiarolo

Reply to
L.W.(ßill)

Thanks, Bill, Matt, and Will. I've got a line on a replacement case from a '99 TJ with only 14k on it, SYE already installed. It appears to have the appropriate vacuum connections, so I'll try to reuse that system first. If it doesn't work out, I'll go with the cable disconnect. In any event, I'll report back to the group how it went and if I came across any issues along the way.

Dave

Reply to
David Pinaula

Go ahead and order that cable disconnect. The TJ cases don't have any vacuum connections, only speed sensor and range light switches.

  • * * Matt Macchiarolo
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Matt Macchiarolo

Reply to
Roy Jenson

Could be, having not owned a YJ I don't know. The 4wd light switch is on the left side, just above the range lever.

  • * * Matt Macchiarolo
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Reply to
Matt Macchiarolo

Reply to
L.W.(ßill)

Just make sure they're both from a 6 cyl, or both from a 4 cyl......or tranny, etc.

4cyl manual are 21 spline input, 6 cyl manual are 23 spline, and all autos are the same but I can't remember whether they're all 21 or all 23.

Paul

Reply to
Paul Keating

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