Bad Driveshaft U-joints and what I did about them...

You may recall my Spitfire had a worrying knocking sound when I bought it...

My Symptoms:

    • Knockety-Knock at low speeds, particularly on left turns, or at other light throttle modes.  No knock under acceleration, hardly any knock on right hand turns.
    • Possibly less knock when vehicle was "cold", i.e. hadn't been driven in awhile.
    • No noticeable knock with the car jacked up and wheels turning (trans in gear).

Common Symptom:

    • "Klonk" on taking up drive, i.e. slack in the driveline.

The Punchline:

    • The knocking noise was one of the main resons I rebuilt my final drive!  Oops!  Hey, the noise was hard to track down!

The Reason for Early Failure:

    • The driveshafts use the same ujoints as the propeller shaft but see 1.945 times as much torque (3.89/2)!  This was a nice cost savings and reduced inventory but it's poor engineering.

Warning!

    Do not attempt this job if you do not have a strong vice with jaws that run parallel and close parallel!  I cracked a set of cups before I realized my vice was closing cocked. Luckily the damage wasn't too bad and I was still able to use the joint.  The cups are a VERY tight fit into the yoke and it will take some pretty good force to pop them in, and I do mean pop!  Once they seat they have a tendency to seat all at once.

The Procedure as I Recall it:

    To remove the old ujoint and cups, release the circlips which hold the cups to the yoke.  Next you will need a big hammer as the way to remove the joints is to beat the cups  out of the yoke using the crosspiece as a drift, (if you can picture that) by holding one part in the vice and whacking the other part with a big hammer.  I can't remember which part of the joint to take apart first, but there's definitely a preferred order.  It will take some convincing for the cups to let go, especially if they've been there for 25 years. Don't worry, the driveshaft is very strong!

    Once you get the cups and joint out, you may find they look like the following:
 
 

This is what my crosspieces looked like!  The upper part is what it's supposed to look like, the lower part shows the grooves worn by the needle rollers.  Note the grease fitting hole plugged with a screw.  My replacement joints didn't have a grease fitting.
Here are the cups!  The cup on the right looks good, the one on the left is garbage!

    Reassembly is in reverse order of disassembly.  Put the cups in the yoke (one pair at a time, of course) and gently squeeze them until you get to the point where if you squeezed them any further you wouldn't be able to get the crosspiece back in.  Install the crosspiece and keep going!  Putting the new joint together is a little tricky - you have to be careful not to let the needle rollers dislodge while you're pressing the cups into the yoke, or you'll crack them or otherwise jam them into the joint.  The key is to slop some grease in the cups before fitting them, the other key is NEVER use any kind of hammering or banging to seat the cups!!  You'll use your vice again in a nice slow manner.  You'll have to use a socket or two as a drifts to seat the cups all the way into the yoke so you can get the circlips in.  They have a tendency to pop in quickly, so be careful and always  check to make sure you haven't disturbed the rollers.  It's not rocket science, you just have to be careful!

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