Fixing a Squeaky Couch?

My couch is approximately 23 years old. I bought it in California. It is lovely and very well made. I had it recovered once about 12 years ago. It has a modern design and has held up so well. It still looks like new.

Both ends have developed a squeak which only happens with the weight from initially sitting down. Thankfully it does not continue to make a noise from shifting positions, etc. I had the upholsterer come out and he opened the liner from underneath to check it out, but could not find any obvious problem.

It does not have springs like some couches do. It is entirely made of wood framework with each section individually tied off to connect it to the next. He said that the problem is with an area of the wood and there is no way to know which section it could be unless I have it reupholstered again. They would have to take it completely apart and apply weights to each section to find which pieces of wood to replace. Any ideas as to how to rid a wood frame of squeaks?

By Glenda from TN