Will a 2003 TJ NP 231 transfer case work in my 1993 YJ?

JaredMLowe76

JaredMLowe76

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I have a ‘93 4.0 5speed

Both front and rear TCase housing is busted, and I am having a hard time finding a new case that is not $1,000 or more or one that won’t take a month to ship. I found one local for $50, but the guy is not 100% sure what it came out of. He thinks it was a ‘03 TJ. It is a NP 231J. What are the chances of that working? Even if I just change the housing and keep all my original guts.
 
If it's the right spline then it will work fine. You'll need to change the front yoke to use your YJ front yoke instead. The 5-speed transmission can accept a long or short tcase input gear, so that's why the spline count is all that matters. You'll need 23 spline, if the TJ case came from a 4 cyl it's most likely 21 spline which is why that input gear needs to be changed if so. So figure out the spline count and go from there.
 
machoheadgames said:
If it's the right spline then it will work fine. You'll need to change the front yoke to use your YJ front yoke instead. The 5-speed transmission can accept a long or short tcase input gear, so that's why the spline count is all that matters. You'll need 23 spline, if the TJ case came from a 4 cyl it's most likely 21 spline which is why that input gear needs to be changed if so. So figure out the spline count and go from there.
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So worst case scenario….it will work, I’ll just have to use the input gear from my YJ to put in the one from the TJ, correct?
 
JaredMLowe said:
So worst case scenario….it will work, I’ll just have to use the input gear from my YJ to put in the one from the TJ, correct?
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Can't do that, they changed the tooth profile of the input gear and the annulus gear that is pressed into the tcase housing. That change happened in mid 1994 model years. So your 93 would have the old style gear, and the TJ would have the new style gear. If the TJ case does not have the right spline, you would need to get the correct spline input gear for a TJ (which would have the proper tooth cut).

Just count the splines in the TJ tcase and see if it's 23. If it is, then you're good to go.

I did forget a few other items: other than the front driveshaft yoke needing to be swapped, the rear tailhousing style is different from YJ to TJ and a different driveshaft accompanies it. So you would need to get a TJ rear driveshaft to go with it. The tailhousing is longer which ends up with a shorter driveshaft compared to the YJs.

You would also need to remove the vacuum sensor from your YJ tcase and install it in place of the electrical light switch on the TJ case. TJs did not have the vacuum actuated front axle disconnect.
 
machoheadgames said:
Can't do that, they changed the tooth profile of the input gear and the annulus gear that is pressed into the tcase housing. That change happened in mid 1994 model years. So your 93 would have the old style gear, and the TJ would have the new style gear. If the TJ case does not have the right spline, you would need to get the correct spline input gear for a TJ (which would have the proper tooth cut).

Just count the splines in the TJ tcase and see if it's 23. If it is, then you're good to go.

I did forget a few other items: other than the front driveshaft yoke needing to be swapped, the rear tailhousing style is different from YJ to TJ and a different driveshaft accompanies it. So you would need to get a TJ rear driveshaft to go with it. The tailhousing is longer which ends up with a shorter driveshaft compared to the YJs.

You would also need to remove the vacuum sensor from your YJ tcase and install it in place of the electrical light switch on the TJ case. TJs did not have the vacuum actuated front axle disconnect.
Click to expand...
Ugh. Okay, how about a 2000 XJ? Other than spline count
 
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