Are you sure it needs replacing?  Have you monitored its performance with a
meter?
  I recently replaced one that had gone more than 200K miles.  It had been
getting a little tired over the past year or so, but I had not been able to
get it out with any normal approaches.  Since the cat recently
disintegrated, I no longer cared whether it got banged around and I wanted
to get it out just to prove I could do it.  I was buying a new cat anyway.
   The hex had rusted away enough that it was no longer 22 mm; even 21 mm
slipped.  I destroyed most of the external part of the sensor and finally
heated the bung around it red hot with a real torch and turned it with a
pipe wrench.  It went about a half turn before things cooled down too much
and I had to repeat the proccess twice more.  The biggest problen was
holding the cat firmly enough.

Have fun,
Larry A.

On Fri, May 16, 2014 at 10:26 AM, Don Hanson <dhanson928@gmail.com> wrote:

>    Is there any special tricks that will help with this?  Mine is due for a
> change soon and the last time it was really an ordeal..Should I run the van
> to heat things up first, or soak it with PB Blaster cold or what?
>