Does anyone know how to reset shuttle valve in the ABS hydraulic inside the frame. I can't get any brake fluid past this part. Tried bleeding it through the bleeder and no fluid. Rear brake/ABS light is on in dash. Just installed new brakes in rear thinking this would cure the problem since they were wore out.

 

I believe the rear ABS sensor is located on top of the rear differential housing. It gets its signal info from the differential ring gear. You might want to check that sensor and the wiring to it. That sensor/signal may be the cause for the light.
If you opened the system at the rear and brake pressure shifted the valve in one direction , the simple fix is to open one of the front lines/calipers to shift the valve back to the center position. Just make sure to keep the master cylinder filled to the top at all times. How are the front pads? Depending on mileage and condition, it might be a good idea to replace the calipers also. Keep in mind again depending on mileage and use the rotors should be trued /replaced if necessary. New pads on rotors that are worn more at the outer edge cannot do an effective job of stopping, and it causes the pads to contact only in a small area of the rotor surface.

 

New calipers and rotors were recently installed by our local mechanic shop. This hydraulic assembly has only one brake line from the MC entering and one line leaving to the rear axle. The front brakes are on a different circuit completely. This is why I'm confused on why i can't get fluid past this assembly. I cracked the line from the MC and fluid came out when there was pressure on the pedal. i cracked the line exiting to the rear, and nothing, pedal solid. Even the bleeder didn't vent out any fluid. A mechanic mentioned i may be able to remove the assembly, dissassemble it to return the shuttle to its correct position, but he wasn't positive. This part is real expensive.

 

It looks like you need to start from the beginning and that is at the master cyl.
With pressure on the brake pedal do you get fluid out of both lines at the master cyl if you loosen them slightly?
If I remember correctly you should have an orange lite for the abs system and a red lite for the rest of the normal brake system.
That red lite can come on with a low brake fluid level, proportioning valve off center or parking brake on.
I believe you can remove the wire from the proportioning valve and if the light goes out then the valve is off center. If the lite still stays on then check the magnetic switch under the master cyl and the switch on the parking brake assy for improper
function.
The proportioning valve has a button on it. It either has to be depressed or pulled out to allow fluid pressure to the rear cyls when bleeding.
This is normally accomplished by the valve itself when sufficient brake pressure is applied and it proportions the majority of the pressure to the front calipers , and this is to prevent the rear brakes from locking up before the front calipers can do their job.