The SD60I (Isolated) "Whispercab" was essentially an SD60M with an improved "isolated" cab (hence the "I") that was designed to minimize noise inside the cab and reduce vibration providing a better working environment for Train & Engine service employees. Conrail purchased its SD60Is as "kits" from EMD, who did not have the production capacity to meet the order at the time. These kits were assembled by the Juniata shops in Altoona. Conrail's SD60Is were numbered from 5575 through 5654, and one exception, 5544. CR 5544 was the first unit designed with the new cab and became the standard for subsequent orders.
The SD60I's are identical to the SD60M's with only a few spotting features telling them apart, the rubber nose seam and reverse mounted nose door.
From my own personal experience, the SD60I is the premier model for sound quality. In notch 8 with the amps in the red, crews can talk at a normal level without having to scream. These cabs are infact so quiet, it's common to have to open the window on occasion to make sure the horn still works!
The units were built with a 2 piece front windshield and 4 piece side windows without sun visors. The side windows are built on an easy slide track design and combined with the tinted glass provide superior crew comfort.