FORD 2013 E-450 v.1 - Manual (Page 136)

Automatic Transmission Adaptive Learning
This feature is designed to increase durability and provide consistent
shift feel over the life of the vehicle. A new vehicle or transmission may
have firm shifts, soft shifts or both. This operation is considered normal
and will not affect function or durability of the transmission. Over time,
the adaptive learning process will fully update transmission operation.
Additionally, whenever the battery is disconnected or a new battery
installed, the strategy must be relearned.
AXLE INFORMATION
Traction-Lok axle (if equipped)
This axle provides added traction on slippery surfaces, particularly when
one wheel is on a poor traction surface. Under normal conditions, the
traction-lok axle functions like a standard rear axle. The axle may exhibit
a slight noise or vibration in tight turns with low vehicle speed. This is
normal behavior and indicates the axle is working.
136 Transmission
2013 Econoline (eco)
Owners Guide gf, 1st Printing
USA (fus)