Reverse/No Forward

Frank Mopar said
904 trans I traded for couple years ago. Itis supposed to be full race setup with Cheetah MVB. Been a running driving car.

Pulled into a parking lot and put it in 2nd. Made a bang, and it won’t go forward in any gear but reverse is fine.

Pulled the pan and it looks fine. Fluid is clean and no pieces are present.

Got the Tom Hand book out and its pointing to an internal pressure leak.

Bummer Mopar Day is Sunday and my daughter run this car. Thoughts? And thanks ahead of time
View attachment 1715965833

Any loose parts in the trans pan, since you already have it off?
I would be leaning toward a planetary issue like mentioned in post 2 or a forward clutch pack or piston issue since it works in reverse. Forward clutch, the rear position with the input shaft attached to it, is applied in all forward gears but not in reverse.
And also take a good look at the low reverse servo in the rear of the trans case. Maybe post a picture of it as viewed with pan removed.