If you have the older narrower drive flanges the splines between the
CV/flange are more prone to wear because they are under more pressure
due to the smaller contact area.
As the joint wears, (assuming equal wear on the CV and Flange) it
introduces slack in the drive train which is best illustrated as
In theory if you have a brand new CV and flange plate they should fit
nice and snuggly together and if you put the CV in a vice and then try
to turn the flange plate on the end of the CV the flange shouldn't be
able to rotate at all.
With a worn CV and flange in the same setup (in vice), you might be
able to move the flange a degree or two back and forth - this
multiplies up through the drive train resulting in around 4-8degrees of
slack. When you add this to slack in the diffs, etc you can end up
with quite thud in the drive train when engaging drive, decellerating,
Now with the narrower flanges, and the smmaller contact area between
the CV and the flange, as soon as you get some wear/movement, the rate
of wear increase and you can end up in a situation where the splines on
the CV and Flange wear away completely and the CV just spins around in
the flange - due to the way the 4wd system all the drive goes to this
wheel and therefore you don't go anywhere, which I think is what
happened to you.
Toyota recognised this issue and introduced longer CVs and deeper
flange plates, essentially doubling the contact are between the two -
with these newer components you still get the wear, but at a much
slower rate so in general now the CV should wear out quicker than the
splines on the end and in the flange plate.
This is why one of the golden rules when replacing the a CV is that you
should also replace the flange plate - if you replace the CV, but
retain the already part worn flange plate, you end up with accelerated
wear of the splines on the end of the CV.
As Chris said, when he had his CVs replaced last year the whole drive
train felt a lot tighter - this is the effect of the new splines.
Hope that helps ;-)
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Cirencester, United Kingdom
1994 HDJ80, 2.5" OME Lift