Transaxle talk

have had a problem for some time on my builder.
Reverse is real hard to do, running or not.
Much as I want it to be a brake problem, I think this is wishful
thinking.
Had the rear brakes off and started it and the rotors spun easily with no wheels on the ground.
Boy try and push it backwards, you would think you hit a brick right away.
When it's running you really gotta gun it to get it to back up.
This is a toronado transaxle (1977), and I am imagining it is some kinda weird "posi-problem"

Just hate to take it to a trans shop for expensive experimenting

it has 4 wheel discs, just replaced the rear with corvette calipers with parking brake. havent even tried/hooked up the e-brake yet, and it did it before I changed them.

forward there is no problem, reverse takes lots of revving up.