Drivetrain vibration/ clunking only on heavy acceleration/ or from a stop

So this vibration/ cluncking seems to be from between the front seats and mostly during off the line acceration, and from all I can find it's the flex disc, but my flex disc shows no signs of damage. Can these discs go bad without looking bad or is this possibly the hanger bearing on the driveshaft?

I am also looking for any other possibilities for the cause of this vibation/ clunking as there sounds like something is hitting the bottom of the car but there are no impact marks to show me where the issue is

So this vibration/ cluncking seems to be from between the front seats and mostly during off the line acceration, and from all I can find it's the flex disc, but my flex disc shows no signs of damage. Can these discs go bad without looking bad or is this possibly the hanger bearing on the driveshaft?

I am also looking for any other possibilities for the cause of this vibation/ clunking as there sounds like something is hitting the bottom of the car but there are no impact marks to show me where the issue is

From what you have described, it sounds like the driveshaft center bearing has failed. It's a moderately hard job, more time consuming than anything.

I'm assuming you have an E32 (1988-1994)? Have a go at this page:
http://bmwe32.masscom.net/sean750/driveshaftCenterbearing/driveshaftCenterbearing.htm

It's an e23, 83.
I was thinking the bearing, but hoping It wouldnt be I guess I'm digging into some fun today
thanks for the info, I've read through the process definatly not gonna be a quick fix but I guess it could be worse, at least the bearing isn't expensive

is it a single knock? could be a mount.and if its the bearing you may want to gt that fixed. the last thing you want is enough play for the u joint to bind.