Rear wheel alignment on 2009 Altima

Question: after replacing rear shocks on 2009 Altima, does in need a rear wheel alignment?
After shocks were replaced on my Altima (without wheel alignment), I drove about 4500 miles. After that the tires were rotated and the back tires installed in front. I immediately noticed loud road noise, mechanic says it is uneven tread wear and I think - this is too much of a coincidence.
So should they have done the alignment when they replaced the rear shock absorbers or not?

Get a 4-wheel alignment done. Any time suspension work is done, you should have an alignment.

Much could depend upon exactly how the rear tires were worn but odd wear patterns will cause a noise that may not be so apparent while the tires are on the back. Once moved to the front it may become very noticeable.

Any odd wear pattern could be caused by lack of an alignment. It could also be caused by the previously worn rear shocks and was exacerbated by the installation of the new shocks to some degree.
Without seeing the wear pattern it’s impossible to determine.

Rear tires usually wear unevenly on FWD vehicles but alignment every two years is a good idea.

thank you all for your comments

It seems unusual to need shocks that soon, but 1 result of bad shocks is often cupping of the tire tread. If you see evidence of cupping that could be a source of the noise also.

Every front drive car that we have owned to recently would wear the rear tires irregularly so that the tires would be noisy when they were rotated to the front if I delayed rotation. For some unknown reason, our latest front driver did not do that when I delayed rotation to over 10,000 miles. The noise that you hear is harmless but annoying. Give it some time to see if the noise diminishes or else goes away. If it does not, diminish after a few thousand miles, it may never go away. I seriously doubt that you need a rear wheel alignment. Rear shocks/struts do not affect wheel position laterally; only control the wheel’s vertical position.

Rear wheel alignment is normally not needed. The only ones that I did were on a 1970 and 1984 front drivers and we have owned more than a dozen front drivers since.