At what RPM do you shift?

1600 going up. Every ten mph less going down.

 

55 to 9 45 to 8 etc to 6th then as truck is slowing down 5th if i let off clutch and still lugging 4th. If still lugging 3rd or 2nd depending if im stopping to take off again snd how much weight im pulling.

 

in the low gears it's 1500 or little lower. 1700 in the higher gears.

i've pulled tank and it would be 1800. you gotta learn to drive and shift when your pulling a tank. not the same experience as pull a dead load.

tanks are harder to gain momentum. and will pull you back. and will shove your forward. if your hauling single bore.

 

I should calirfy i haul refers.

 

If you double clutch you can shift on the low side 900 rpms and the high side around 1200 it will help save fuel.

 

I shift up at 1400 at downshift at 100rpms. but it can vary with motor. I drive an acert cat it likes low rpms, I cruise at 1200 rpms. a Detroit likes them a little higher. ive driven some mechanicals that was high rpms for shifting. you have to figure out whats best for that motor.

 

I drive a 13spd pete 387 my company said 2 use progressive shifting it consist of changing gears at the lowest possible rpm in low I shift 1100-1200rpm and high 1200-1300rpm if u don't go up in the higher rpms like 15,16,1700rpm up there u burn a lot of fuel lower rpm shifting burn less fuel on my truck I used progressive shifting and rolled at 60mph depending on how heavy load was I got up to 7.3 on heavy 35000 up and 8.5 one time I got 9.2 this is on loads 30000 below at with 60mph so shift at lowest rpm possible to save on fuel

 

If you have a 1970's 318 Detroit (two stroke), anything less than 1800 RPM is lugging it. If you have a new Cummins anything over 1400 is too high. Get the engine model number from the side of the engine, go to the MFG website and find the peak torque RPM, dont worry about horsepower. Shift at peak torque on flat or downhill grades, shift at progressively higher than peak torque RPM for steeper grades. When you complete your shift you want to be 400 RPM below peak torque with 13/18 speed. You will lose more speed on an incline so go a little past peak torque so that when you complete the shift you are in the bottom of the torque range.
I see drivers go 400 RPM past peak torque (up to 1800 with a new Cummins) then when they are done with their shift they are just at the top of the curve... Makes no sense. It may make sense in a gas engine because you want to shift in the very center of the torque and horsepower curve (split the difference) but a diesel engine does nothing with horsepower, its all torque.

 

Like Guntoter said, lots of variables. My old school big cam cummins doesn't make any power until 1,600rpm. I run it up to about 2k every shift. But if you're pulling tanker you will have to shift around the slosh.