Washer still won't spin after replacing coupler

My husband replaced a broken coupler on our Whirlpool top loader washing machine. At first there was a burning rubber smell, but I still let it run through and even got it to wash and spin through a few loads - the smell went away. Now it is back to not spinning again. There are SO many threads here, that I am confised. How do I know if it a bad clutch, transmission, drive block, lid switch (if I can get it to run with sticking a toothbrush in, does that rule out lid swicth problem?)… brake shoes, shocks?

Is it possible to narrow it down at all? I can take it apart, but how do I know which to order and replace if I don’t know how to tell what makes it "bad"?

Any help that you can offer will be much appreciated. I am nearly at the point of calling Sears since this has been causing trouble for a few weeks already!