Is there any way someone could post the Trane Service Bulletin about TXVs that cause a water hammer sound. I noticed in another post today that Southern Mech stated something on this issue. Our five year old system works fine other than the water hammer sound on first stage. System was installed in June of 2007 and is a cooling only system with gas furnace. XL19i and XV90 furnace. Model numbers are 2TTZ9036B1000BA (condensing unit) TUY080R9V3W6 (gas furnace) and TXC036S3HPD0 (indoor heat pump rated evaporator coil) Installing dealer has been back a few times since installation, but once unit is run in second stage and drops back down to first, noise disappears long enough for them not to hear it again during the service call, but after running in low stage on mild days, water hammer sound happens again. Very annoying on an otherwise very quiet system.