Driveshaft Length

I picked up an XJ that came with an RE lift and Rusty's long arms. I have no clue which exact kit it has, but its enough to clear 35"s and the guy said he added longer shackles and extended the coil bucket to add enough room.

I went over a speed bump a little fast yesterday and had a loud clunk happen under my feet yesterday. I'm guessing it's the drive-shaft compressing too far. It only seems to have about 2" play. Is that too short for a flexible suspension? If so, I can get that resolved.

Front or rear? Do you have a SYE ? If not you need one. If anything its not compressing the shaft too far, its extending too far...

The noise was from the front I believe. I have an SYE. The clunk happened on compression not decompression of the suspension. If it extended too far then the clunk would likely have been followed by a clanking as the two pieces disconnected from the shaft extending, right?

chances are it was a CA bushing, sway bar link, or panhard bushing.... 2" should be plenty, the stock driveshaft only has about 3-4" of play. and you wouldn't feel that in your feet, since it would hit the transfercase which is behind you.