Changing from 3.73 to 4.10 gears
Hello all, After towing our new Reflection 320MKS from Eastern Iowa to Estes Park Colorado and back, I need more power for the hills. I have a 2015 F-250 with the 6.2 Liter engine. I have 3.73 years...
Forum Discussion
Our Kenworth is a tridrive double framed truck designed for very heavy work. It has a much lower speed final drive. Top end for this truck is about 75 mph. We use this truck mainly off road. The other is a highway tractor. It is comfortable rolling down the highway empty at 90 mph but when it is left parked in the dirt with 100,000 lbs hooked to it, it has a hard time getting itself moving.
Once on the highway and up to 65 mph both trucks perform pretty much identical. I run through the gears often skipping at least one gear on every shift and often skipping two gears when unloaded. The flat HP curve of these engines coupled with 18 speed transmissions means I have no trouble keeping the engine output at 550 HP no matter the road speed.
My 440 HP Ford pickup on the other hand only makes 440 HP at 6 specific speeds ... 2800 rpm in each gear. If the Powerstroke is revved to 3200 rpm in 3rd prior to shifting to 4th the power will likely have dropped to somewhere around 390 Hp prior to shifting and after the shift, at 2400 rpm, the engine will still only be making somewhere close to 390 HP with the throttle to the floor. More gears or a flatter power curve would allow the engine to produce closer to the rated 440 HP at all highway speeds. This range was much larger even a few years ago. The huge torque of these new pickups means they do have a significantly flatter power curve than they used to.
Edit: I've noticed that when climbing hills the Powerstroke likes to hold onto gears longer. For instance when pulling up a grade with my Ford, the Torqshift would make best use of the Powerstroke's power band by dropping out of 4th gear at 2300 rpm. Instead it will hang onto 4th gear and let the engine pull down below 2000 rpm. I don't mind this at all but I do think that the shift points of the Allison/Duramax are at higher rpms, making better use of the Duramax's power and contributing to its success on the Eisenhower hill runs.
Once on the highway and up to 65 mph both trucks perform pretty much identical. I run through the gears often skipping at least one gear on every shift and often skipping two gears when unloaded. The flat HP curve of these engines coupled with 18 speed transmissions means I have no trouble keeping the engine output at 550 HP no matter the road speed.
My 440 HP Ford pickup on the other hand only makes 440 HP at 6 specific speeds ... 2800 rpm in each gear. If the Powerstroke is revved to 3200 rpm in 3rd prior to shifting to 4th the power will likely have dropped to somewhere around 390 Hp prior to shifting and after the shift, at 2400 rpm, the engine will still only be making somewhere close to 390 HP with the throttle to the floor. More gears or a flatter power curve would allow the engine to produce closer to the rated 440 HP at all highway speeds. This range was much larger even a few years ago. The huge torque of these new pickups means they do have a significantly flatter power curve than they used to.
Edit: I've noticed that when climbing hills the Powerstroke likes to hold onto gears longer. For instance when pulling up a grade with my Ford, the Torqshift would make best use of the Powerstroke's power band by dropping out of 4th gear at 2300 rpm. Instead it will hang onto 4th gear and let the engine pull down below 2000 rpm. I don't mind this at all but I do think that the shift points of the Allison/Duramax are at higher rpms, making better use of the Duramax's power and contributing to its success on the Eisenhower hill runs.
