The inner CV boot on the front right axle shaft is starting to degrade on my 2003 2.0L Escape, so I want to get a new one on there. I've read that once you've prised the shaft out of the transmission, I have to replace the snap ring/retainer thing that sits right at the end of the shaft at the transmission end, I shouldn't reinstall it with the old one still on there - is that correct?

 

When I did my alternator the first two times I removed the axle and did not replace the snap ring. I never had an issue at almost 300,000 miles.
That being said, if the ring is only s couple bucks and you're already at the store why not get one for peace of mind?
But I would not say it is a must.

 

Echoing Scott91370, I had both sides of my '02 out and never changed the ring. Didn't appear to be an issue.