1999 N14 525hp rpm calculation check

Spicer Transmission Ratio RPM Calculator

You said standard 22.5, as in 11R?
If I'm wrong change the tire height to 40" for 295/75 & 275/80 22.5

I'd be in 16th more often than not. Be spinning the back box constantly in 17th not saving much fuel & creating more heat for the cooler to deal with..

16th
17th
18th

 

Right on. So it seems going 75-80 empty I could be in 18 high. I don't think I'll have an issue since it's a 18 speed and nice to have the option to always drop rpm I suppose.

 

Maybe 80-85 actually but still haha

 

18th at 1500 rpm and 11r22.5 with 2.85s



No longhand calc
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lower RPM does not always equal better MPG. Watch your boost pressure, keep it low. you can get better mileage at 1700rpm cruising easy than say 1200 and lugging

 

Right on. Any other tips for fuel economy driving tips now that I'll be forking the bill? I've heard slow and light in the throttle and I've heard the engine works most efficent with the pedal to the floor so I'd be curious to hear what you all got to say. Thanks for the information shared so far

 

I've also heard the newer engines like the dd15 are obtaining better mpg by running at lower rpms. The older engines do not perform as well at lower rpms or what is this all about. If it wasn't for eld I'd prolly go with a dd15 instead of a n14 or detroit 12.7

 

Drive like you have a egg under fuel pedal.

 

It really depends a lot on what you will be doing. 2.85s might be ok for all highway driving with your gross weight always being lighter than 80,000 lbs., but if you are ever going to have to start a heavy load in soft conditions or on a steep incline you may end up spending all that you saved in fuel in one repair of the clutch, driveline, or rear ends.

 

I don't think I'll be getting 80k started on a steep incline with a 700hp pimped out cat . What is soft conditions? Like dirt? You really think I wouldn't be able to pull 80k with a N14 and an 18 speed with a 2.85?