Allison Transmissions

Allison transmissions are truly automatic. There is no clutch, a torque converter is used for shifting. These transmissions come in a variety of series and are specific to the application they will be operating in.

The series are defined as:

•    1000/2000 – Class 6 & 7 vehicle ratings

•    3000/3500 – Class 7 & 8 vehicle ratings

•    4000/4500/4700 – Mostly class 8 ratings

Within the series are sub-classes:

•    HS – Highway Series (no PTO provision) typically not for vocational applications

•    RDS – Rugged Duty Series (has PTO provision in MOST cases)

The series are divided into close ratio (series ending in 000) and wide ratio (series ending in 500). The 4700 is a unique product, it has the gear splits of a close ratio, with a deeper low 1st gear and additional reverse, effectively making it the widest ratio. 

Every engineering department runs a SCAAN, an operational report that aids in determining which torque converter will be used and what rear axle gearing is appropriate for the customer, prior to build. The proactive approach is to contact your Allison rep and have them run a local SCAAN, along with a suggested axle ratio. If the engineering SCAAN does not allow for the same ratio, and nothing about the spec differs form your communication with Allison, be sure the question the change. Allison is the rep for your customers, they know their product. Perhaps engineering misinterpreted a piece of data. Better to settle on paper than in iron.

These transmissions do a great job and are installed in the lion’s share of vocational medium-duty trucks. They require less skill from the driver and, in general, are easier on the equipment. Shift modes, FuelSense, and Acceleration Management programming add to the versatility and attractiveness of these products.

There are some functional differences between 1000/2000 series and the larger. And 4700 requires a manual shift to get into deep reduction.

If you’re unclear which product meets your needs,

contact Gary.