Hi all,
The day is soon approaching when I go out on my own. Got my truck running and driving good but I wanted ask guys who’ve been around longer about this. My truck has a 350hp 3176B Cat, 8LL trans with a final drive of .74 and a 3.91 rear end 11r 22.5 tires all around. Not specs for a highway truck which is fine with what I’m doing but im at 1700 RPM at 60mph and 1800 at 65, so I’m concerned about fuel efficiency. Fuel efficiency is one of the only things besides weight the 3176 has going for it.
Looking at my engines specs max power is at 1800rpm but max torque is at 1200rpm, I’m guess right in the middle at 1500rpm is the sweet spot but I don’t actually know that. Haven’t drove the truck anywhere near enough to have any real world data on that either. From the specs I’m right in the power band but I’m assuming that’s not good for my MPG. Is that the case?
Want to hear other o/o’s perspectives on this and what they would do. In the long term I’d like to get a 13 or 18 speed in the truck eventually but I’ll be stuck with the 8 speed for awhile. Look at other transmission specs the final driver ratio is similar to the 8LL so I wouldn’t gain top end speed there but it would be more pleasant to drive.
Thoughts?
Looking at engine specs and transmission for fuel efficiency
Discussion in 'Ask An Owner Operator' started by Cdubb, Dec 28, 2021.
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Something ain't lining up with the specs you've given. Even put you on low pro 22.5 as a tire size. Could be on tall 24.5's for that matter..
shooter19802003, Brettj3876, Cdubb and 1 other person Thank this. -
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Spicer Transmission Ratio RPM Calculator
Hopefully that works.?
I just put Spicer gear calculator into the search bar if the link is no good..
shooter19802003, Flint1, Oxbow and 1 other person Thank this. -
So far so good, other than the cloud of blow by that forms around me at a stop light, & a PIA coolant leak that I was aware of before purchase.. lol
But I've only put about 11,500 mi on this one.. Thats what the IFTA quarter is looking like. At 75k gross & tall it was looking more like 6.5mpg over a 1500 mile run WI-FL.. I generally look for light weight freight though..
Make no mistake, a 350 is slow getting up to speed, but miraculously somehow she aint the slowest in the hills compared to the neutered company slugs roaming the super slab..
Also ran a 11.1L 350 Detroit for about 3.5 yrs. Apparently I've got an affinity for 11 liter, 9 speed FLD's..
That Detroit would swing 1800-1900rpm for hrs on end if i needed to be someplace. The M11 I'm only comfortable at ~1750 sustained. Both are weak below 1400, which is where I downshift if pulling hard.. Never ran a 3176 Cat, so you'll just have to find where she likes to run..
The Detroit saw a best quarter of 9.08mpg & worst of 6.62mpg really whipping on her. Its said a high hp motor will be more efficient when driven properly, but if you take it easy these little guys can do well too..Tug Toy, shooter19802003, Brettj3876 and 3 others Thank this. -
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