noise when trans is in reverse

New build, T400 rebuilt by good shop, When I put it in reverse a loud screching sound, sounds like the flywheel is hitting a bolt...only happens in reverse. If i go back and forth several times it will almost go away, then the next time I start the car and put in reverse it is there again in full force. the torque converter bolts are tight. any ideas?

 

My idea- don't put it in reverse

 

If like some automatics I know, reverse is applied by high gear and low gear clutch packs. If metal to metal screaming/s****ing is heard, it is an internal problem that cannot be fixed without major surgery of the transmission.
If I know as well as a transmission I killed, if driven, you will need to pay your favored transmission builder for the "core" he has to drag out to save some of it's guts and case along with yours to build another good transmission.
Pucker up and smile. $$$. Pretty simple.

 

Gee Wizz........thanks, I never thought of that!! That will really help.

 

It may just may be a valve body problem. When in reverse the hydraulic line pressure is at it's highest. You might have a valve or check valve rattling giving you an odd noise. MY 2 cents

 

The 400 uses a reverse band that is applied by a servo. It may be that the band it's self is doing the squaling or it may be due to another part slipping or rubbing when the trans is put in reverse.

I couldn't find a Turbo 400 power flow chart online to tell what is or isn't turning when the reverse band is applied to tell what is turning an what isn't but when some of the transmission guys wake up they might have some good answers.