I have a craftsman 18" ratchet that they no longer make and do not offer repair kits for any longer. In fact to my knowledge they no longer make anything like it and I was offered a smaller one when I asked about the warranty. I love this ratchet enough I have acquired 2 of them but I use them almost daily so I wanted to repair this one.
I took it apart and found the reason it was not holding was the spring under the ball that hold the ratcheting mechanism in place was broken. Also, the ball had a flat spot worn on it that could also cause it to slip. I am sorry I did not think of taking pictures when I started this project, so I will just use the same pictures of me putting it back together to show the procedure for taking it apart. Please note it was much dirtier when I started. I cleaned the ratchet and inside parts with an ultrasonic cleaner(carb cleaner would have worked almost as well though).
Step 1: Start the Teardown
Take the ratchet apart.
Use a pair of needle nose pliers to remove the retaining clips and slowly pull the back of the ratchet apart. Be careful not to loose the ball. You will find a spring in the hole located in the handle of the ratchet.
What you see in the picture is a ball from a ball bearing that happened to be the same size. As to replacing the spring I just got lucky and found one in my spring drawer. Hopefully yours is not worn out or you can find one the same size.
Step 2: Finnish the Teardown
You will find a retaining clip on the front of the wrench as well, holding the rest of the parts in, just remove it and pull the gear. The wrench is now completely apart.
Step 3: Clean and Lubricate
Clean all of the parts and coat them with oil for lubrication. I used fluid film as it prevents rust and does not dry-out like most stuff. I can also say the wrench has never felt smoother.
Step 4: Start Reassembly
Put the front of the ratchet on first so that it will be easier to keep the retaining ball in place on the back.
Step 5: Put the Back Together and Replace the Clip
Notice where the ball goes (the spring is below the ball pushing it up to hold the ratchet in the same direction)
Finnish the assembly and enjoy your ratchet.
Most good ratchets are under warranty but maybe you just want to make your favorite ratchet work a little smoother. This is less then the gas to take it back for warranty. Or you could be under the same problem I have and can not get it replaced anymore and need to fix it.