I was noticing a high pitch turbine sound when driving at speed the past few weeks.
Trans fluid was about a quart low (small drips on the driveway..) so I topped it off Saturday.

Today while driving ~40 mph it just went bang and went out of gear. Now it won't engage ANY gear

Any guess what broke?

 

Probably your wallet... :-)
Is the shifter loose or is it still attached to something? I don't know much about the innards of transmissions but the shop manual may help if you have one.

 

Maybe the front pump or the pump drive dog 'ears' on the torque converter sheared.
I had a buddie at the Jag dealer that had the pump fail that way on the BW66.

If you are near DFW area of Texas I could give you a really good deal on a BW66 gearbox that I have had sitting in my 'pile-o-parts' for YEARS!!!!!!!!!!!!!!

bob gauff

 

Yeah, sudden fail sounds like a drive thing as opposed to bands or clutch.

The whine suggests a failing pump.

Perhaps it is time for a GM conversion with OD!!

Decades ago, I could not give my leftover but healthy BW 66 away. Finely, I found a guy that took it and the busted engine as well. Pleased wife that it was gone out of the driveway. But, the LT1 was there getting prepped for the install!!

Carl