'95 Grand Cherokee - 129k miles, WA car so virtually rust free.
Inline 6, I think the normal grand Cherokee trans, don't remember the transfer case but it has part time 4wd and all the modes - 2wd, 4hi, 4lo, N

Hey all, hoping someone can help me out as I don't really know what else to look at.

Early this morning I was driving up a paved mountain road in the dark and all of a sudden hear a pretty loud thunk from what seemed to be the the middle of the car, followed by what sounded like a cyclical squeaking/light grinding that seemed to be connected to the wheel speed. The noise went away after a couple seconds as I slowed down. The thunk didn't sound like something breaking/cracking, more dull sounding. I was on my way uphill on a fairly narrow road so I didn't want to stop then so I went pretty slow until I found a good spot to stop. The noise came back once before I could stop, but went away after a few seconds again as I slowed.
Once I stopped, my first thought was "****, I hit a rock" but I could not see any sort of impact mark anywhere on the underside. The pumpkin/driveshaft are the lowest spots out front and there's nothing there. If I smacked a rock going 40 I think it would have made a pretty good dent or at least left a mark. I kept going and made it to the top, no more noise. Grabbed a flashlight and looked around underneath, the only thing I saw was that it looks like the front driveshaft has extended by about 1" (see the attached pic for that to actually make sense) judging from the grease lines. I also think it was leaking a bit more oil than normal, but that might just have been in my head since I just did the valve cover gasket. It was also a longer run than usual at faster speeds, so I think the leak from the oil filter adapter gasket had more time to get all over the place.
At this point I go on a hike since that's what I was there to do. Came back to the car later in the day and checked out everything I could in the parking lot, all seemed fine. Gingerly took off and no noise. Kept going back down the way I came, got the squeaking/light grinding noise once for a few seconds after going over a bump, otherwise nothing. Can't tell exactly where the noise came from. Made it 100 miles home at all speeds and everything was fine the whole way, besides that couple seconds. Power delivery ok, shifting as ok as a 25 year old 4 speed can be, nothing out of the ordinary. Got home, tried 4 wheel and that was ok too. The only thing I can see right now that I need a bit of a sanity check on is the transfer case; it looks tilted and I swear it wasn't like that before (see pic again). Is it supposed to be like that? The engine seems to have the same bit of a tilt so it makes sense it would all be inline. I can't fine any stressed/bent bolts anywhere; t-case to trans, trans to crossmember, trans to engine, engine mounts. Everything seems fine to I can't imagine the whole transfer case tilting wouldn't have caused issues somewhere else in the chain. What else should I look at? Drive shafts both seem straight, mount points seem ok, I don't know what else to look at! I feel like if it was something major with the trans or transfer case I wouldn't have made it 100 miles home. My only thought is something with the front driveshaft and diff getting misaligned and maybe 4wd wasn't actually working when I tested it. I did pull the fill bolt on the transfer case and it happily spilled out very fresh looking/smelling trans fluid so it's not empty.

TL;DR
Loud thunk, followed by squeaking/light grinding noise that went away. Made it 100 miles back home. Can't find anything obviously wrong beside maybe front drive shaft being "extended" and transfer case maybe tilted. Need a Jeep Sherlock Holmes to put together the clues.


Grease mark at bottom of photo makes it seem like drive shaft has separated.

 

I'm thinking the transmission mount is broken allowing the case to rub on the crossmember and the exhaust pipe was rubbing on the frame as well. Just my thoughts and something to check. It's not uncommon since it tends to get soaked with engine oil and transmission fluid easily.

 

Damn, first one, I think you're right. IIRC the mounts are usually more... circly.. than mine is.

 

Well, I replaced the trans mount and it definitely helped with some vibrations at idle but the transfer case is still tilted. The increased leaking I noticed is actually trans fluid off of the bottom of the bell housing. Good little puddle of it on the floor after letting the car sit overnight. After some googling I found it could be from the trans pump/seals. Can the rear main also leak trans fluid? What would the noise have been from? Could the pump have violently died in some way that caused a good thunk? There's still no noise when I drive though and it runs and shifts fine so it doesn't seem like anything terrible is going on with the trans.
Another odd thing; my ebrake is smoother now/easier to set/unset. Still works fine. I have no idea how that could be connected.

 

Trans fluid leaking out of the bellhousing is a sure sign of a failed torque converter input shaft seal. It's simple to replace, but requires separating the engine and trans, pulling the converter out, putting a new seal in, and reassembling. $2.00 seal, 8-10 hours work. That seal holds full pump pressure supplied to the converter from leaking.

Your transfer case normally sits at an angle to the frame to lessen the angle of the driveshaft to the rear axle. On high lifts, you sometimes have to put spacers in the crossmember mounts for a "t/case drop" to stop vibration caused by the increased driveshaft angle.

You might want to pull the rear diff cover and check the carrier for cracks. The rear diff on my WJ blew up because the carrier case cracked around the planetary gear shaft and the shaft fell out locking everything up. I got warnings a couple of days before with a weird "Clunk" sound twice and I didn't pay attention to it, much to my sorrow. That little chunk of grey cast iron was the piece that held the shaft bolt in.