Posted by Paul Cook on Sunday, October 06, 2002 at 10:13PM :
In Reply to: OT... I hate to do it..... posted by Jonas. on Sunday, October 06, 2002 at 8:03PM :
This is not exact science! The tachometer reading of my 3.54 in fourth gear and that of a friend with 4.10 gears running in fifth (OD) seems to have both trucks at comparable engine speeds. Maybe someone will do the math for a more exact comparison.
The point is that I can run in fourth with a load and have close to the same engine speeds and fuel economy as a 4.10 in OD. Most of the time, the Cummins pulls my 3.54 well in OD and I get the fuel savings. When I need the extra power, I just drop down into fourth. It's about the same as shifting a two-speed rear axle.
An advantage of doing the harder pulling in fourth gear is that the transmission is working "straight through" and has no internal gears carrying the load. This minimizes the transmission drag, reducing heat and wear.
When I pull, I pull. The rest of the time I enjoy great mileage.
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