Difference between 4 & 5 speed Alllison Transmissions

[CoachCrazy]

What is the big difference between a 4 speed and a 5 speed Allison transmission? Are there more gears to get to drive/overdrive ? Or something else ?

[The Newell]

More gears normally allows a higher top gear and a lower low, while keeping plenty of mid-range flexibility. A four speed generally has two lower gears, necessary to get it moving from a dead stop or climb steep grades, and then two fairly high ones for city and highway. That tends to leave a fair performance gap between 2nd and 3rd.

Hope this helps,

Joseph

[express1]

Originally Posted by The Newell

More gears normally allows a higher top gear and a lower low, while keeping plenty of mid-range flexibility. A four speed generally has two lower gears, necessary to get it moving from a dead stop or climb steep grades, and then two fairly high ones for city and highway. That tends to leave a fair performance gap between 2nd and 3rd.

Hope this helps,

Joseph

That was a very simple and direct answer....very good, for me anyway.... What about the mode switch. Can you explain that simply.... or does it just hold gears longer?

[GORDON HUMMEL]

Allison has 2 transmission that are used in Newell type vehicles. The older HT740/750 is a 4/5 speed unit. Top gear is one to one & the lower gears have a multitude of ratio's available depending on the application. Some 5 speeds actually start out in second unless overridden. The later transmission, the World transmission comes in may variations, but for high end coaches, the HD4000/4060 are popular. Most are 6 speeds with 5 & 6 being overdrives. These units can handle almost all the larger 4 stroke engines available today. The 4 stroke's are much happier @ a lower RPM than the old 2 strokes.

You can use the link below to find out specific data on later models

http://www.allisontransmission.com/m...tion/index.jsp