2000 Tacoma 4x4 Auto Tranny Knocking

Hi,

I'm wondering if anyone else with this vehicle experienced a problem at
100K miles with the tranny. Seems to make a slight banging noise when
it revs down at ~750 rpm (idle) and gets faster and eventually goes away
by 1000 rpm. It sounds like metal hitting on metal inside and back by
the bell housing. Two different mechanics listened and looked and one
said it sounds like the torque converter and the other said it might be
the flywheel is broken.
Either way it'll be expensive because the transfer case is below the
tranny but I'm wondering if anyone else has seen this and if it can be
tolerated foe maybe a few more thousand miles until I trade it away.

I've done all routine maintenance including the 90k overhaul and changed
the oil every 3k.

Thanks,
Bill
2000 Tacoma 4x4, 3.4L 4 spd auto TRD package 103k miles.