Technical How broken is my transmission? (sbc, nv3500)

Hey all, wanna get some opinions since I wont be able to pull the motor again till next week, but....

5 days ago the truck ran fine, no transmission clunking at all, but I had a small oil leak from the pan, so I had to pull the engine and replace the oil pan. I replaced the oil pan and reinstalled the motor today. All went smooth. Motor runs great now, but taking it out for a test drive I heard the crazy clunking sounds you hear in the video below. It also felt like the gears were loose (like I could move the shaft around while with the shifter) while I was moving. When I parked it, I started rocking it back and forth like in the video. The clunking only happens if the truck is in gear. It happens if the clutch is engaged or not, but only if its in gear (any gear), the sound sounds like its coming from the bell housing. Is it possible that its something with the clutch itself? I doubt that I blew up a transmission by taking out and putting back an engine, especially since it went back smooth enough that I was able to do it all by myself.

Any theories?

 

Are you sure the noise is not in the rearend

 

100%. First thing I checked was the u joint and the rear end, but its definitely coming from the bell housing or the trans itself.
Also, putting it in neutral and rocking it, no noise.

 

Did the pilot bearing come out and fall maybe?

All FW and PP bolts secure?

 

Is the fork properly engaged with the throwout bearing?

 

Dust shield on the front of the bellhousing hitting the flywheel?

 

did you leave out the transmission mount bolts?

 

clutch fork spring left off? or shift rods misaligned , something left in the bellhousing? either way you need to pull apart and inspect.

 

Welp, its worse than I thought. I pulled the motor. Clutch, flywheel, pilot bearing all look perfect and new. The transmission, now with no motor on it, does have a tiny bit of play, but nothing out of ordinary, but tracing it back looks like my Richmond quick change rear end ate it:



I'm preeeeety sure that a diff isn't supposed to have THAT much backlash. I still don't know why the sound was coming from the bell housing, but isolating each component, this is where the failure was. This sucks, cause rebuilding a Richmond quick change (if even possible any more) is gonna run me way more than the trans. Im still trying to figure out how the hell this happened... I guess I'll post an update when I drop the rear end and tear into it.