In Allison four-speed transmissions, technicians discuss the number and arrangement of planetary gear sets. Who is correct about the structure described as three interconnected planetary gear sets named the front, center, and rear?

In Allison four-speed transmissions, technicians discuss the number and arrangement of planetary gear sets. Who is correct about the structure described as three interconnected planetary gear sets named the front, center, and rear?

• A. Technician A
• B. Technician B
• C. Both Technician A and Technician B
• D. Neither Technician A nor Technician B

Answer: (A)

Allison four-speed transmissions make four forward speeds by a compound arrangement of three planetary gear sets that are interconnected along the gear train. This setup is commonly described by position as front, center, and rear, which simply indicates their place in the train and how torque flows through them when different clutches are applied. Because the gear path goes through all three sets in sequence, engaging the correct clutches yields the four distinct forward ratios from a single input. technician A’s description matches this standard three-planetary, front-center-rear arrangement, so it’s the correct description for how these transmissions are built. The other technician’s description would have to imply a different count or a different arrangement, which doesn’t align with the typical three-planetary, interconnected layout used in these transmissions.

Allison four-speed transmissions make four forward speeds by a compound arrangement of three planetary gear sets that are interconnected along the gear train. This setup is commonly described by position as front, center, and rear, which simply indicates their place in the train and how torque flows through them when different clutches are applied. Because the gear path goes through all three sets in sequence, engaging the correct clutches yields the four distinct forward ratios from a single input.

technician A’s description matches this standard three-planetary, front-center-rear arrangement, so it’s the correct description for how these transmissions are built. The other technician’s description would have to imply a different count or a different arrangement, which doesn’t align with the typical three-planetary, interconnected layout used in these transmissions.