If you go to www.shotgunworld.com
and in the Ithaca forum you can find the Model 37 take down guide. The guide is actually in steves pages but the forum is a direct link to it.
Please note when taking down the Model 37 the butt stock MUST be removed before trying to disassemble the action. Pressure from the stock locks the triggerplate screw in place as if it was loc-tited in to place.
You will find that the Model 37 has less parts than any other pump gun made. This all go's back to when the gun was designed. Original concept was from JM Browning and then improved at Ithaca.