Beak, that is a common, if not universal, problem with those SMx Olympias and it's easy to fix. There are four rubber washers between the outer shell and the inner works and they have collapsed with age; this lets the moving parts fall far enough to drag on the shell.

You will see them from the bottom of the typewriter, towards the corners, between the painted shell and the frame, held by large screws. Use rubber washers about 1/8 or 3/16 inch thick (diameter doesn't matter much) from your hardware store's plumbing department. If you replace them one at a time, you won't have any trouble keeping things aligned.

Have Fun with your rejuvenated SM4!

I know this is an old thread, but for anyone reading it, here is my observation:  A problem like this, and I've run into it quite a bit on lots of typewriters, would make more a grinding than growling sound.  I have fixed grinding sounds, and the consequent dragging carriage, with washers this way.  A true growling--the sound the carriage makes when there is no dragging shell pieces or anything like that, is usually caused by little tiny ruts in the carriage track.  I've seen this especially on Royal and Smith-Corona portables.  I've even seen in on the front tracks of the old Underwood SX-100 machines.  Even my ol' 1952 Royal HH had such wear on a rod in the back that rested on a wheel.  On that one, I just grabbed a pair of pliers and turned it about a quarter turn.  On the other carriage tracks, I did a little sanding with some coarse-grade steel wool.  Sandpaper will work.  Both methods you have to watch whatever falls down into the machine and clean it out when you're through.  It takes a little time getting them smooth again, and you might have to make a compensatory adjustment or two, but in the end, the carriage will sound as smooth as it did when it was a young typewriter once again.