TBSS_Ron

I'm looking at a 2007 CTS-V with 81k miles.

When I was driving it around in stop-and-go traffic, I heard a
clunk-like sound when taking off. Is that normal, or is
the rear or mounts or something going out?

When I was under the hood, I noticed that all pulleys are
spinning smoothly, except for the crank pulley. It appears
to wiggle a little. Is that normal or is the harmonic balancer
on it's way out?

Thanks for any/all help,

FuzzyLog1c

iTrader: (4)

That clunk on acceleration is the sound of the rear differential bushing needing to be replaced. Polyurethane replacements cost about $50 from Revshift or Creative Steel, however, it's pretty annoying to get them out. Creative Steel rents a tool that makes the job easier, but the Revshift bushing is better designed.

The GM crank pulley wobble is a pretty common problem. You'll definitely need to replace it. At the high end, you've got the ATI Superdamper (P/N 917266) which normally costs $400. Every once in a while ATI sells blemished units on eBay for $250 shipped. Check this thread for more info. Of course there are vastly cheaper options as well.

jmilz28

iTrader: (13)

Very common clunk could be any or a combo of the diff bushing, engine mounts, tranny mount, carrier bearing, or flywheel. do you have a repair and maintenance history on the car? do you do your own work? You should be able to visually check all the mounts above if you can get it in the air.

BudRacing

iTrader: (3)

I would say those are just the tip of the iceberg.