What happens is the rear bushing that is in the tube farther back begins to leak as the seal is 60 years old is leather. On the few I took apart, the front bushing and rear seemed to be okay but if they run without oil then the bushings can be egg shaped and more leakage. Once the seal begins to leak then oil goes into the diff making the axle seals leak then gets onto the brake lining. The trans and u joint get starved of oil and begin to wear also. The oakie bushing replaces the two bushings and seal on the original setup. The front bushing comes out and the oakie bushing goes in and the rear bushing will be pushed back, like Jerry said. You only get one attempt, so measure the oakie and compare with the original bushing size as some need to be tweaked. Check that the yoke fits in the bushing also. 1951 should not have the dowel pin but check if there is one. Then it needs to be removed so the old bushing can move back if it needs to. To help with install, you can freeze the bushing and warm up the tube when pounding it in. Use a block of wood and grease up the splines and make sure they are not sharp. You may have to smooth them at the end so no damage to the seal is done. There are a few youtube videos you can look at on the net that will give you an idea of what you are up against.
