When you bled in new fluid, did the old fluid come out rusty? If so, some calipers may be binding or tubes might be plugged w/ rust. If you didn't bleed, then that alone is a problem since should be done every few years, unless using DOT 5 silicone fluid like me. Good brakes should be able to skid the tires, and all 4 evenly. The tires stop the car, and braking to just before skidding will stop the fastest. If your front circuit isn't working, you will only get 30% braking capability from the rears.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans