One of the mechanical repairs on our '51 Chevy Fleetline was to fix the transmission leak at the torque ball.  We had already checked out the problem, narrowing it down to the shim/gasket in the torque ball collar at the transmission.  Chevy used this torque tube system from 1918 through 1954 as did Buick, Nash and other auto manufacturers.
        The basic reason for the torque tube (enclosed drive shaft) is to stabilize and give rigidity to the drive line.  The torque tube generally consists of a torque tube, torque ball, gaskets, shims, retainer, retainer seal, and a seal at the differential.  Our '40's and '50's Buicks have a more complex torque tube setup than the Chevy.  The Buicks require the rear end to be fully pulled back, giving only a little over an inch clearance between the torque tube and the transmission, making repairs tight and difficult.  On our '49 Roadmaster, we removed the entire torque tube and rear end several times before we finally figured out it could be done by pulling the rear end back toward the rear bumper using heavy duty ratchet straps, and that was before we had a lift!.  That's a lesson we wont have to learn again!  Fortunately, this Chevy was a lot easier.
        Before starting work, we got out parts together, ordering a new torque ball and a shim and gasket kit (when ordering the shim kit, remember that car shims have 4 bolt holes and truck shims have 6 bolt holes).  We put the '51 on the lift and our good friend and car restorer Robert Wiley came by to help.  Jeff Coe and I were working on other parts of the car while Robert took on the torque tube project.  With all of the parts laid out, Robert began by unhooking the emergency brake cable and pulling it back out of the way, then propped up the torque tube to keep it from falling down as he began to take it apart.
                        HERE ARE THE STEPS HE TOOK:
        1. He removed the cap bolts from the torque ball collar and unscrewed the torque ball retainer ring from the torque tube, then pulled the torque ball back over the torque tube.  This exposed the U-joint at the transmission.
        2. Tapped back the locking tangs on the U-joint bolts.
        3. Unbolted the U-joint by removing the back half of the trunion bearing, making sure to mark which way it would go back together.  This separated the drive shaft from the transmission, allowing the torque ball, shims and collar to be removed from the car.
        4. Next, he cleaned up the parts and put a new seal in the collar (tapered end forward), coating the seal in oil first.
        5. Then replaced the torque ball retainer ring-seal (at the torque tube).  If this seal is bad, transmission oil can run down into the torque tube.
        6. Robert now put the 4 new paper shims over the torque ball, followed by the collar, and slid it back on the torque tube to be test-fitted later.
        7. He then aligned the propeller shaft yokes together and installed cap screws, bolting the front U-joint back together, bending tangs on the locking plates to lock down the bolts.
        8. Now he pulled the torque ball forward over the U-joint and slid the shims and collar over the ball and tightened down the cap screws, first one finger-tight, then tightened the diagonally opposite bolt 8-12 ft/lbs, then re-tightened the first bolt to 8-12 ft/lbs, then all bolts to 8-12 ft/lbs.  
        9. The test for the torque ball is that it needs to be firm, but not too tight.  To test, put both hands on the torque ball and if it can be moved and is snug, it is properly adjusted.  If the torque ball can not be moved, or is too loose, then add shims to tighten, or remove shims to loosen.  After this adjustment, Robert tightened down the retainer ring.
10.  Last, hook up emergency brake cable and check transmission oil level.  We had to add more 90-weight mineral oil.  We never use multi-viscosity oil in these old transmissions and rear ends.  It can cause premature bearing failure.
        After the test drive, there were no leaks and we had the ole Chevy singback in our transmission, having saved it before any serious damage was done by running dry.
        A closing thought:  We have had severe weather here in the South, with driving rains and flooding.  When the sun finally came out, we were all so glad to see that we and our cars had survived, that we got them out and started driving them.  I saw more old cars than I had seen in years.  I got my '64 Sting Ray fastback out--a car I hadn't driven in 6 or 7 months, and made plans to make driving the old cars a regular event.  I hope as time passes that the old cars won't be put up because the scare is over.  Theres always something that comes up that makes it easier to take the driver,but it's worth the effort to get the old car out!  See you next month, and keep 'em driving!