Sorry for the late reply, I have very limited internet access.
I'm now pretty certain it's the 2-3 piston needing replaced. The 1-2 was pretty easy... I understand this one's behind the valve body. How do I get behind there? Are there any balls or springs that will fall out if I start removing bolts?
If I happen to find a broken spring in there like I did with the 1-2, should I go with the same colour one?
1996 Thunderbird LX (4.6), previous daily driver
1995 Mustang GT (5.0), daily driver
1995 GMC C2500 (5.7), alternate daily driver