Just to clarify, those driveshafts listed by Salad list the collapsed length next to the part number so you wouldn't want to match your measurement from yoke to yoke with one of those lengths, correct? You would need to allow for some compression in the driveshaft slip if measuring while at rest, right?

and on a side-note, I've actually seen a double cardan driveshaft with a slip-yoke on the TC output end for sale on Ebay. That had me confused for a minute, not being an expert. That would eliminate the need for a SYE but isn't really much better than a TC drop from what I can gather, though.

When I measured a rough mock-up to see if the IRO hack'n'tap would work on my 99XJ with AW4 and np242, I found the common front XJ shafts were a bit too long. They would end up fully compressed with the vehicle at rest, so I'd have to find one of the shorter ones listed, closer to the 30" collapsed length, or just order a custom one. Still haven't decided what to do since I live nowhere near a JY and was hoping to not spend $300 on one driveshaft...

 

If i get the complete kit from iro with the driveshaft...its guaranteed to fit right? Providing i hack and tap correctly

 

If you order the driveshaft with the kit, I think they will send a pre-sized driveshaft that will fit most XJs. The new shafts they use have a good slip length so it will be forgiving if dimensions are a tad off. To get the best fit, have them send the hack n tap kit first, install that, then get your measurement. If you have them wait to send the driveshaft, you can send your measurements and they can send a custom shaft, if I'm not mistaken. I was emailing a guy named Zack at IRO when I was trying to figure mine out and he was a huge help. Definitely send them a message if you have any questions or are decided on using their products, and they can tell you how to guarantee the best fit! The problem is that XJs are not all identical so guaranteeing a fit involves measuring your particular rig.

The generic-length XJ shaft they were going to send me if I ordered the HnT with it at the same time, would have been too long for mine. I woulda had to cut all the splines on the output shaft completely off to have any extra compression, so it wouldn't have worked for me. Mines a DD so I can't really do it the correct way since I can't wait around for a driveshaft to be built and mailed after spending a day doing the HnT to get the actual measurement.

I still have no idea what I'm gonna do with mine. For a bit I was considering getting a used 231 and rebuilding it with a short-shaft kit to use with a stock front driveshaft in the rear. Lately though, I've been leaning towards just taking a week off from work so I can do the IRO Hack n Tap properly and spend my money on a custom driveshaft instead of another transfer case and kit...