AW4/transfer case swap questions

ok, i currently have an '89 with a 242 (21 spline). something in that combination is blown up, and I want to ditch the 242 for a 231 for more aftermarket support, and this is going to be a trail only rig anyway. i have the trans and 242 from a '92 (i think), and they are both 23 spline. i plan on grabbing a 231 from a junkyard to put in there.

here are the 2 questions:
the '89 has the power/comfort switch. i remember hearing somewhere that i would need to switch valve bodies to keep this? i really don't care like i said, this is a trail only rig. is that just a slide in swap for the aw4?

second question is will the 242 cross member work with the 231, or should I grab that with the transfer case at the junkyard?

:repair:

The power/comfort switch just tells the transmission computer to act a little differently. The tranny should swap over just fine and work with the existing electronics. Only difference is the output shaft spline count as you noted, and the 4th gear ratio is slightly different.

I believe the cross-member will work as well, since it supports the tranny and not the transfer case.

What are your symptoms, btw. The AW4 tranny is pretty reliable and most of the problems are on the electrical side of the house and not mechanical in nature.

The crossmember should be the same (it was on my '91)

The power/comfort stuff should be controlled by the TCU, so it should still work (I will know in a couple of days if it still works on my '91)

lawsoncl said:

The power/comfort switch just tells the transmission computer to act a little differently. The tranny should swap over just fine and work with the existing electronics. Only difference is the output shaft spline count as you noted, and the 4th gear ratio is slightly different.

I believe the cross-member will work as well, since it supports the tranny and not the transfer case.

What are your symptoms, btw. The AW4 tranny is pretty reliable and most of the problems are on the electrical side of the house and not mechanical in nature.

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The jeep was being dolly towed by the previous owner when it went into gear and locked up the rear wheels. my guess is that it went from TC neutral to 4x4 (ouch) it still drives, but makes a grinding noise now, i believe the problem is in the transfer case. if I am going to swap it, i might as well go to a 23 spline, especially since i got the 23 spline AW4 from my cousin for free.
the crossmember is a little banged up, i might as well just grab a new one anyway. i think i am the 9th owner, so god knows where this jeep has been. the poor thing is going into retirement in terms that it isn't going to be driven on the road anymore, but it will probably be driven harder by me than any other owner...

Ah, yeah that sounds like a mechanical problem.

ehall said:

The power/comfort stuff should be controlled by the TCU, so it should still work (I will know in a couple of days if it still works on my '91)

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It doesn't appear to work with the '94 tranny I swapped in. I'm not 100% on that but I couldn't feel any difference in my limited testing.

After a bit more testing, it actually does seem to be there, but it's not nearly as noticeable. Before, having it in Power would run the RPMs way up and then it would shift fast and hard. Now, the RPMs still go up a bit higher than Comfort, but then the shift is smooth like in Comfort mode. I'm guessing that my '91 TCU is still controlling the shift points according to selection, but the tranny logic for quicker shifts is missing.

Would you want to sell the spare 242? I also have an 89 with a cracked/bombed 242.

ehall said:

After a bit more testing, it actually does seem to be there, but it's not nearly as noticeable. Before, having it in Power would run the RPMs way up and then it would shift fast and hard. Now, the RPMs still go up a bit higher than Comfort, but then the shift is smooth like in Comfort mode. I'm guessing that my '91 TCU is still controlling the shift points according to selection, but the tranny logic for quicker shifts is missing.

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The throttlebody->tranny cable affects the internal hydraulic pressue, and hence the shift firmness. You might find re-adjusting that cable at the throttle body helps firm things up.

I played around with the TV cable and while it does change shift pressure like it should it is universal. With the old tranny Power had much firmer shifts, while Comfort had slow smooth shifts. Now they are the same for both.