big let down car will not move now

You need to determine whether this is

1....some weird mechanical problem like a broken rear axle

2...Wheel interferance

3...Brakes locked up

4...Transmission problem

+++++++++++++++++++++++++++++++++++++++++++

A....Jack up front wheels. Make sure they turn freely. If not, remove wheel, determine if wheel(s) are binding on caliper(s)

If not is front brakes locked? If so, this is likely a master cylinder problem

B....Jack up rear axle. With both rear wheels off ground, trans in neutral, and parking brake released, can you turn either wheel? If not remove wheels. Wheels may have a problem hitting / bending etc

Can you "wiggle" the wheels that is do they seem free but taking up play in the rear axle? Look at the driveshaft and work the wheels one way / the other. Any movement in the drive shaft?

C....Transmission.....Does it "feel" like it's going into gear, IE can you hear the engine lug down? Give it gas, does it feel like the torque converter is loading?

CHECK THE TRANSMISSION fluid. In neutral.

D....If all else fails, take a pan / rag and briefly crack each tube coming out of the master cylinder. See if there is pressure there.