1966 Mason & Hamlin B has a groaning squeak when the sustain pedal reaches full travel. If pressure is put on the pedal horizontally toward the bass while pushing down, the groan goes away. It sounds like wood on wood to me.
Replacing the felt where the vertical rod meets the back of the pedal had no effect. Removing the lyre and opening the pedal box, there are four small wood blocks holding the pedal bushings. The outer block for the sustain bushing was contacting the inside edge of the pedal box. I was able to insert a thin piece of felt (with some ProLube for good luck), and the groan is gone -- at least for now. See photo attached.
I also lubricated the return springs under the keybed, which pushed on leather, but I'm glad to hear other usual suspects.
--Cy--
------------------------------
Cy Shuster, RPT
Fairfax, VA
http://www.shusterpiano.com------------------------------