I just got done looking through Dr. Friedman's book.

1. There is no mention of problems with the steam plants.
2. The Navy was not happy with the initial 5"-54 guns. On the shore bombardment role the Shermans were not seen as good as the simpler to operate dual 5"-38 on the Gearing class. The automated 5" - 54 did have initial reliability issues.
3. The follow up Adams class had better freeboard and were designed to take the early Tartar Mod 11 missile launchers vs the modified Forrest lighter single arm Mod 13

Points:
The vast majority of the FRAMed Gearings were scrapped by 1980. All were out of USN service by '83.
The same time the last of the Gearings were decommission/sold was by '82/'83. That was when the Shermans started to be decommissioned.
The Adams class didn't start to be decommissioned until the very end of the 1980s. The end of the Cold War accelerated the decommissioning & scrapping.

Observations:
1. The FRAMed Gearings were at the end of their operational life by 1980.
2. The Shermans were replaced by Perry class frigates.
3. The Adams class had a full service life.