I dug up an old tech article.......try this its great ............1994-2001
This is for changing out your rear brake cylinders from a ¾ ton to 1 ton cylinders. First thing you need to do is go to your local auto parts store and ask them for GM part #4637337. DO NOT tell them you want GM 1 ton cylinders for your a ¾ ton Dodge. You will only confuse them. They sometimes will tell you that they have a cheaper cylinder or a higher quality one. I chose the higher quality one and paid around $80.00 for the pair, but they do come with a lifetime warranty. Might as well grab a couple cans for brake cleaner while your there at it because youll need it.
Go home, block the front tires and jack the rear of the truck up. Place jack stands under the axle and remove both tires. Next you will need to remove the brake drums. They usually dont come right off. What I did was take 2 lug nuts and spun them back on the studs on each side. I started the truck, put it in reverse, got the rpm up and hit the brakes hard. One drum broke loose, but the other didnt. I had to take a heavy punch between the studs and strike it with a large hammer. It broke loose finally.
Your drums will probably not slide right off. Back off the adjusters a tad and it should slide off. Spray the parts down with brake cleaner and get things cleaned off. Now is a good time to look at your brake shoes while you have the drum off too.
You will need to remove ONE spring from the shoes to allow it to spread apart so you can get the cylinder out. (See Illustration) It is only necessary to remove the forward spring, meaning the one facing the front of the truck. This will free up the shoe so you can remove the cylinder.
Take a 3/8 wrench and remove the brake line from the back of the cylinder. Take a 13mm wrench and remove the two bolts securing the cylinder to the housing. Remove the cylinder.
The 1 ton cylinder is noticeably larger.
You will need to reuse the metal pieces that spread the shoes. (You will see when you do it). Put the new cylinder in, tighten the bolts and install the brake line back in. Also secure any springs that you removed. Put the drum back on and adjust the brake adjusters until the just barely drag on the drum. Start the truck and bleed the air out of the system. Put your wheels back on and your ready to go.
I had been battling hard pedal for almost 2 years and figured it was in my master cylinder/booster. After doing this my brake pedal is soft and I have awesome brakes now.
