I have done a lot of mechanical work in my lifetime. Numerous times, the problem wasn't where I thought it was. For example, I have a 40-694. It started making noise also. When you rotate the tension lever, it pulls a rod that leads to the back of the saw. Delta (and Dewalts) don't leave enough clearance internally for the rod.
I removed the switch & tension lever. The bottom of the rod was hitting a piece below it. Take a chainsaw file and file a notch below the tension rod.
Another time. mine sheared a bolt located in the back (internally.) It was a design flaw that put the entire load on an undersized bolt. The one on the end of the connecting rod (not the end on the motor shaft, the other end.) The outer end of the bolt sheared and it was still sawing, but it rattled. I went to a local hardware store and replaced it with a stainless steel bolt, which is harder. Problem solved.
Ike, with all due respect to you, and others, DO NOT get hung up on a "Tension Number." Each time you clamp the blade, it is slightly higher or lower in the clamp, making your tension number meaningless. More importantly, when you thread the blade through the wood and clamp it, the drilled hole in the wood isn't in perfect alignment with the 2 blade clamps. Now you are "wasting" the first part of the tension by pulling the wood into alignment. To learn to tension, without any wood, practice tensioning by the amount of pressure you need to get the blade to "ping." After you have learned how to do that, when stack cutting, you will now find that each time you tension, you end up with a completely different number. Scrollers would do themselves a favor if they covered those silly tension numbers with a piece of tape.
jerry