[TR] Universal Joints: What is the Reason for Replacing

[Anthony Rhodes]

I had 5 of 6 that were bad in my old TR4a.  The driveshaft had a nasty 
vibration.  When I got under the car I saw that the yokes of the driveshaft 
were not aligned properly.  I thought to myself  "Ah Ha!!  That is the 
reason".  So I realigned the yokes.  The problem was MUCH MUCH worse after 
that.  It felt like the driveshaft was going to fly out of the car!

I then FELT the U-joints.  THey had some very palpable play when I tried 
resisting back and forth rotation of the opposite side.  I could feel a ton 
of play.

I took the drivehasft to a truck driveline place and they replaced the 
U-joints.  They had to fiddle with the spread of the yokes to get the 
perfect flexibility of joints too.  Then they also found that the shaft was 
terribly out of balance.  They fixed all that and it was fine.

After that I was quite attuned to little jolts in the driveline.  I felt 
more, but very subtle, unevenness.  It was almost like an irregularity in 
the pavement.  It took me a little while to convince myself it was not my 
imagination.

I then felt the play in the joints on the half shafts.  I could JUST barely 
feel a slight "click" of play. I took out the half shafts and tried to take 
them to the driveline place.  It turned out that the guy who worked there 
moved to the main shop in a town 40 miles away. So I did hte job myself.  I 
did not tune the yokes, not balance the halfshafts, but it turned out OK.

When I looked in the old cups I could see that the rollers had worn little 
ruts in the cup and spider.  It seems thay roll back and forth rather than 
around and around.  It appears that they fail by making ruts. 3 of the 4 
joints were worn out.   BTW, the joints in the mainshaft were so bad that 
the rollers were BROKEN!

So, I'd say, if they are old and there is any doubt, just replace them.  I 
bet the new ones will be tighter.

-Tony

> What has been curiously lacking with the discussion on the list so far is:
> WHY replace the U-joints at all?  WHAT symptom would you be trying to
> eliminate? WHY are new U-joints even necessary?