4spd vs 6spd Allison question.
If I can find 2007 Chev/GMC 3500 with the 8.1 I would like to think about picking one up. I drive my 2002 by the tach, 65 mph=2100 rpm. That seems to be the sweet spot for best mileage. I know I am...
Forum Discussion
minnow wrote:trail-explorer wrote:ramyankee wrote:
Driving the 6 spd might give me a slight increase in mileage because of the 2 extra speeds.
Extra 2 speeds compared to "what"?
All 8.1 engines were paired with the Allison transmission, which was either a 5 speed or 6 speed. 6 speed was 2006 and later I believe - at least that was the case on the Duramax / Allison combo.
2005 and earlier was 5 speed.
Correct. On the 8.1 gassers the 6th speed was introduced in 2006. Prior years had the 5 speed. The difference was rather inconsequential.
The Allison was the only transmission available if the 8.1 was selected on the order sheet.
Both the 8.1 and the Duramax were also available with the ZF-6 manual transmission.
