X15 Efficiency vs Performance

Nope not at all lol. Frozen/refrigerated. Just was trying to maximize the fuel economy without sacrificing to much performance but it seems its one or the other nothing in between

 

Ya, that's what they seem to say a lot of the time. But with 2.64 rears and no mention of the input torque rating of the trans, it can get spendy right quick like. If someone spec'd a truck new enough for the X Cummins, and at 400, the rest of the components were likely spec'd accordingly. Putting 2150 lb/ft in low gear to 2.64s is a whole lot of twist'n going on. But 1650 at 2.64 is likely a good match. That efficiency governs at 1750 rpm. I have it in my 2021 Pete 567 at 500hp, 3.25 rears. I wouldn't mind a bit lower numerical rear gears. At cruising speed, I'm at the high end of the "efficiency" rpm curve. That is according to the gauge anyway. I'd likely be happy with about 3.08s or so.

 

Probably spot on with that assessment but I wasn’t thinking anything crazy where the components wouldn’t tolerate it, like 50hp and up to 1850tq. I hear 3:08 with a 13 speed is the way to go. But those are few and far between in my searches

 

Choose at least 450hp go ex rating or smart torque don’t go for standard one I prefer you ex rating with hd driveline.

 

I’d go minimum 495-505ish HP with the cummins, especially if you’re pulling grades often. We know somebody who bought an itty bitty DD13 motor (first mistake), and with the small engine tied to the terrain he pulled, it worked the ever living piss out of that truck. The time it spent in the shop was a result of that as well.

 

2020 w900 565hp 2050torque heavy haul truck. 18 speed manual . Double frame. 46k rears. 4.30 gears . Pulling a walking floor trailer 75k to 85k most of the time. Sometimes heavier if the woodchips are wet. 2 hr round trip on some decent hills. About 20 min of pto time per load. Avg 5.5 mpg. Bumps out at 72 with stock rev limit. About 1800 rpm and stay their most of the trip. Doesn't even slow down hardly on any hills maybe 1 or 2 mph. Pretty impressive since on the same hills our 99 w900 with a 10 speed. 4.10 gears and 550hp 3406e drops About 8-10 mph on the same hills with the same loads

 

yikes. But wouldn’t expect anything more doing heavy haul. But your making the big buck you can afford that economy lol