While valve gear was the initial suspect of the locomotive's inconsistent running, further analysis revealed that both the valve gear and motor were running consistently. This led to the identification of a minor split in one of the locomotive's gears. Thankfully, a spare gear was obtained from Peter's Spares, as part of a syndicated order with one of our fellow enthusiasts experiencing problems with their J72 fleet. Insertion of the new gear resolved the issue in what turned out to be a rather complex diagnostic process.
The 38xx has been pressed back into service, providing additional freight capacity to the Western Region.