I finally tackled the PTU replacement last weekend and I'm happy to report that it appears to have taken care of the "happy dolphin" noise. Oddly the howling/rumbling is still present, but I'm kind of wondering if it's due to the tires since I really only notice it on the freshly re-paved road near my house. I need to spend more time trying to track that down.
On my Lincoln MKS I was afraid I might break the bolts that hold the catalytic converter to the turbo, so instead I opted to remove the exhaust flex pipes (where I did break a bolt). I quickly realized that the PTU would not come out through the available space. I'm really not even positive that it would have fit even if the catalytic converter were removed. So I removed the entire subframe and honestly, for as little time as that takes, it makes the job MUCH easier and opens up the entire area to reach many of the bolts. If I were to do it again (which I hope to never have to) I would drop the subframe before removing the passenger half shaft and PTU bolts.
One tidbit that I never did find in any of the videos I watched - the steering shaft is keyed at the steering rack so there's no need to mark the position before dropping the subframe. But you WILL need to keep the steering wheel from moving once it's disconnected from the rack to avoid damaging the clockspring. Oh, also the connectors for the electric power steering are a lot easier to access once the subframe is lowered a few inches.
After I made sure the new PTU bolted up correctly I opened my old PTU, which I drained and filled with Lightweight Shockproof fluid probably 10k miles ago. The fluid was still liquid, but it was very stinky and dark black. The fluid change was too late to save the PTU, and all the roller bearings for the middle shaft were gone, similar to what so many videos show. So many videos that it kind of makes me wonder if the bearings were ever actually installed to begin with. On mine the bearing race is still intact, but no rollers were to be found.
-Rod
