FBinNY 

First off make sure the chain is long enough to loop the big/big without pulling the RD up to it's stop post. The chain is so much stronger than anything it loops, so if over-tightened it'll destroy whatever it has to.

Now check that the RD is low enough (B screw setting) that the upper pulley never can touch a sprocket through the chain. If you thing yours might be too close, try lowering it a bit and see if it helps. You can always reset it later.

Here's a way to make a poor man's gauge for checking if the hanger and RD are vertical. It's not as good as the tool, but a damn sight cheaper. You'll need a reliable straight edge long enough to span the rear wheel, and a short ruler. Shift ti a larger sprocket, but it doesn't have to be the largest. Set the straight vertical against the wheel, and measure out to the top and bottom loop of the chain. The distance will be the same if all is truly vertical, otherwise you'll need to bend the hanger to correct. Note that this doesn't measure horizontal twist, but that isn't as common a problem.

Most hangers can be gently bent by putting an allen key in the RD's mounting bolt and horsing it over a bit.


Otherwise your problem could be caused by a stiff link in the chain or a stiff pulley, among other things.