Crazy noise between engine and trans
 

2000 WJ jeep, 4.0L, 42RE, 4x4, 214,xxx miles. Long story short; My good ol' 00' WJ lost reverse, I investigated the issue and rebuilt the overdrive unit on my 42RE. Filled the trans and transfer back up with ATF+4 and everything ran great; I had reverse back and shifting through all gears was smooth and firm. Fast forward one week later, my wife is driving home from work in the jeep and as she was going up a small hill she lost power. RPMs shot up and the jeep would not go forward any more. Once I got to where she was to try and determine the issue I discovered that the jeep had no motion in any gear (ie: forward, reverse, o/d off, transfer switched in all settings). When the throttle is pressed there's a crazy noise coming from between the engine and trans; it sounds very similar to if you ran out of power steering fluid an the pump was grinding. Once the jeep was towed home I thought I'd have to push it into the garage, but damn I was wrong I backed it right in. So, the issue is only intermittent. I'm not too sure where to start. So far I've begun taking the flywheel cover off and taking a look. Anyways, has this happened to anyone before? What could my issue possibly be? Thanks to all in advance, everyone on here seems pretty knowledgeable

Welcome to CF!

This same basic thing happened with my 89 Chevy truck with the 700R4 transmission. What happened was the turbine wheel in the torque converter shattered when climbing a hill slowly and there was a whine-like noise and the truck lost all forward motion. I backed down the hill and tried it again, but it wouldn't move at all after that. That sent tiny bits of metal throughout the entire transmission so I had to completely rebuild it.

Usually what happens to a torque converter is the stator blows and the vehicle looses most of it's acceleration, or "becomes a dog" as the saying goes. It still drives, but just won't get up and go.

Yours may have lost the forward clutch in the transmission. That's just behind that snap ring in the overdrive unit.

That happened to me on my first trans swap eons ago but it was because I didn't fully tighten the flex-plate bolts. They got sheared and my flex plate was wasted, all in an afternoon. Nice mess. Good lesson...

Nice catch! I hope that's all it is. Come to think about it, I had this same thing happen to one of my other trucks because the bellhousing bolts were loose. The center fractured out and stopped driving it, then after shutting it off it worked perfectly until you gave it enough gas for it to slide over the cracks and stop driving again. I nursed it home and took it apart. The center section was broken out but it indexed enough to drive it lightly.

^^ This