I've recently installed a RE 3.5" lift kit with full leafs on my 99 XJ and now I have pretty noticeable vibrations in the driveshaft. I want to put a SYE and new DS on but after 2 days of searching online I've found that almost all of the Heavy Duty kits all say they are for the NP231 only. I found the Iron Rock hack-n-tap kit and am leaning towards doing that and ordering the DS they offer as well. I don't live near any JYs so the cost of a new DS is not that bad considering the gas & time it would take me to get a used one and the cost of rebuilding it.

Am I missing anything or are there really not many options for a SYE on a NP242?

also, I've already tried a 1" tc drop with minimal benefit

You can only do a hack and tap on the np242.

Thanks! Do I have to worry about spline count on the yoke or are all 242s on the XJs the same?

Not true-- Tom Woods has a main shaft replacement. Its is not the HD type, but it does come with a DC Custom Driveshaft for $470.

Or a HnT for roughly $90...

Thanks for correcting me. But for that price you can pickup a np231 with a 4:1 kit...

tom wood's 242 kit is a stock mainshaft that he "hacks and taps" on a bench then sends to you. he also charges a core. i ran a "hack and weld" 242 sye using a 3103-27CV yoke. worked great.

Hack & weld? I don't trust my drill skills either.LOL.

Use a ruler to draw a line thru the center, use splines to make sure you have a straight line that passes thru the exact center of the shaft. Make another, creating a perfect X.

X marks the spot to drill..

Or just leave it idling in reverse as you *carefully* drill. Will hit center every time. Same trick to use when trimming the output splines with a side grinder and cutoff wheel. Idling in reverse and you get a perfect slice.

broke the tap inside the shaft and said **** it.

idk why people keep saying theres some voodoo magic about leaving the shaft spinning and the drill automagically finds center. it was no easier then using a center punch and drilling without it spinning.

a 4" lift on my 98 w/the 242 caused bad vibes too,i did the iron rock h n t , w/a new driveshaft done by a local shop. works great .

Yeah, I didn't say it was cheap...

Hey thanks for all the help everyone! I'm pretty sure I'll be going with the IRO Hack'n'tap kit and just order the driveshaft they offer at the same time. $250 for a new DS is a pretty good deal from what I could find. Only thing I'm worried about is drilling the output shaft and tapping it without breaking something off inside the shaft. I drilled and tapped the steering knuckles on my old XJ cuz I found the brake mounting holes were stripped, so I'm pretty sure I can pull it off as long as I'm careful and don't try to rush things. Plus I like taking my 4.5" grinder to things and saw the write-up about having the shaft spinning to get a square cut. I'll probably get the drill guide/jig dealy from IRO too just to be on the safe side for the drilling.

Any other tips/trick for the IRO hack'n'tap would be much appreciated, and thanks again everyone!

Thought of another question: Since the lift kit I just put on is new should I let the springs settle a bit before I do the H'n'T? I'm worried that if I do it before it settles and it decides to settle a lot, the measurements for cutting will have been off and the new DS won't have enough compression room on the slip joint. So should I worry about that and if so, how long should I wait for things to settle out? I've thrown all my tools and a bunch of heavy stuff in the back to give it some weight and help things settle a bit...