Are the legs rusted on the washer? You can lay the machine down, use a penetrating oil to soak into the rust - or - heat them a little and try to break them free with a wrench. Don't force them or they will break off, causing a lot more work. I've had pretty good luck with penetrating oil soaking in for a day or so. (I know, you don't want to stop using it ;-) Once you get them free, you can try to clean them up with a wire brush. If they are too far gone, take one into the appliance parts store and match it up with new ones. IIRC that GE washer legs fit the unimatic. I try to use Maytag rubber cups for their dryers as they are the correct size and the Maytag rubber is the best for keeping them tightly held in place on the floor.
The unimatic is one machine that must be on solid footing or it will shake and walk all over the place. Shims will not work for long, been there, done that ;-) The only way to make it work properly is to restore them properly - you'll be happy you spent the time to do it right.
