Delayed/Harsh Forward engagement and a burnt C1 clutch in Aisin AW 60-41SN transmissions can often be caused by excess wear at the C1 damper piston bore. Because the piston acts as an accumulator for Drive pressure in Forward gears, it is very active in the bore. Leakage past the piston due to bore wear causes loss of Drive/Line pressure, and allows pressure spikes to reach the C1 clutch.
Restore normal Forward operation and revive accumulator control by installing Sonnax C1 damper piston kit 19741-17K.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.