if I remove my drum brakes and replace with disc do I need to remove the residual valve ? if yes , how do I remove the master cylinder ? thanks Tim

Pretty sure you have to remove the residual valve, but not 100% certain. You live in the CINCI area I would call DRY DOCK over off 747 they deal alot in trailer parts.

Some just use an ice pick to poke thru the end and rupture the valve w/o disassembling the MC.

Yes you need to pull out the valve. Its just a matter of pulling the snap-ring out of then end of the master cylinder with the plunger, removing the piston, removing the valve and re-assembling in reverse order. To remove the master cylinder from the coupler, remove the brake hose, take out the four bolts (number 17 on page 9 of the Dico 10 doc below), slide the master cylinder out of the back of the coupler.

Tim - What coupler do you have Dico 10 or 20? They are similar, but the 20 has an extra roll pin and guide pin.

Here is a parts breakdown for each:
Dico 10 - http://shop.easternmarine.com/downlo...an_model10.pdf
Dico 20 - http://shop.easternmarine.com/downlo...ator2.6923.pdf

Oh and you'll also need a reverse lockout solenoid and a 5-pin trailer harness to actuate the reverse lockout solenoid when going in reverse with the disc brakes.

us1 , thats it , I was wondering if that was an option . I don't want to have to pull the coupler apart . thanks Tim , also I do have a reversing valve

Can you use the same actuator when switching to disc? I thought drum actuators wouldn't work with disc brakes?

yes you can , but you need to remove the residual valve in the master cylinder or poke a hole in it to let off the presure off the disc brakes , so I am told . Tim