NP231 Krawl Box Install In An XJ

J.C.

J.C.

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Apr 18, 2005
Location
Greensboro, NC
Thought I would cross post this for those that maybe don't read the Build thread but might be interested in the krawl box install.


For those that might not know, the 231 kit gives you an adapter plate, clocking ring, block off plate for where you cut the front output off and a custom output shaft.

Here is what the krawl box looks like after you cut the front output off of the front half of a 231 tcase and weld in the block off plate.



The krawl box adds 8" of modified 231 tcase between the stock transmission and transfer case.



 
The added length created two small problems. The transfer case was now behind the transmission/tcase hump in the floorboard so a small piece of the floor had to be cut out.



The other problem with the added length was that the front driveshaft would now hit the cross member. I simply cut a section out of the cross member and welded in a piece of 3/8" plate. If this doesn't prove to be strong enough or doesn't give enough clearance I'll modify it again.



Of course, the added length also caused the rear driveshaft to have to be shortened and the front driveshaft to have to be lengthened. Not a problem, just more work :)

The krawl box shifter mechanism ended up in a convenient location underneath the cab and I just went straight up through the floorboard with a piece of 3/8" rod from the stock shifter plate. A piece of 1/2" pipe provides the handle for a simple push/pull T-bar shifter. It's a little long so I'll cut it off before I weld on the handle.



The stock transfer case shift linkage was lengthened using just a piece of 1/4" rod bent on the ends to go through the stock shifter plates. You can see both tcase shifter link mounts here.



The krawl ratio with the AW4 (2.80:1), 231 Krawl Box (2.72:1), 231 transfer case (2.72:1) and stock axle gears (3.55:1) is 74:1. Most of my web research indicates that the automatic transmission torque converter provides an effective further 1.8-2.3:1 reduction for a final krawl ratio around 150:1. With 33" LTBs this should be sufficiently slow so that I don't feel too different from the 205:1 krawl ratio of my other rig.
 
Ive thought about this in my tj but its just too long. Good write up, though. How much ya got in it?
 
It can be done. SPOA87YJ has one in his Wrangler! Kit runs about $600, I got the 231 for the krawl box for free. The rest is just work :)
 
Yeah but my rear shaft is 16.5" c to c riding. If I stretched the rear out to about 105" I could get away with it.
 
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