Quote:
Originally Posted by SCOTI
You seem to be fixated that the 6th gear will yield better mpgs. It possibly will, but how much actual improvement will you see and if you see it @ what cost? You really need to consider your return on investment.
I did a quick Google search for rpm calculators. A typical T-56 has a .50 6th gear. That ratio would yield about 1350rpm @ 70mph w/3.73's & your 32" tires. A carbed sbc/bbc is going to want 2000-2200rpm to be happy chugging down the road efficiently @ 70mph. Going up to 4.56's still has you under 1700rpm. There are optional aftermarket t-56's that offer different gear ratios (like a .67 6th gear) but the cost increases w/them.
Lower rpm does not mean automatic better mpg's. It will be quieter & there will be less wear on the motor but it's not a definite that mpg's will improve. They could actually get worse because the motor is lugging to push a brick down the roadway @ 70mph.
Yes, 6pds work great for late model fuel injected cars w/ much less frontal area & weight. But it's not likely that you'll get 2-3mpgs improvement over any other 5spd OD.
The motor needs to be efficient while being able to offer good torque production @ 2000-2200rpm. A 350 w/some GM Vortec (or similar) heads, a decent comp ratio, hyd roller cam spec'd to offer optimum torque @ the calculated rpm, dual plane intake, tuned carb, good ignition, a good 2.25-2.5" exhaust, & synthetic fluids front to rear will all help you.
You want the best mpg's? Here are good questions for you:
What kind of truck (year, type, etc...)?
What mpgs would you like to get w/the "ultimate' combo in your truck?
What is your current mpg average ("it sux" doesn't tell us much)?
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Well I'm glad that I've asked, I had no idea that they needed to be at 2000-2200rpms to be happy. I know that american powertrain offers a close range t56 magnum that has a .62 as the 6th gear, same cost as a wide ratio with a .50 6th gear. I need to know what would be the best for the ride and gas mileage.
Honestly, "resale" value, i do not care about one bit, I'm never going to sell this truck, I do not like new cars and I like these old trucks. Do I want to spend an astronomical amount of money? No but, I'm okay with spending a good bit of money to have reliability, performance and good gas mileage. I'd like to go for road trips across the country at some point in this truck.
As far as your questions go, 83 c10 silverado.
I'd like to get upwards of 20-25 mpg, with a fuel injected small block chevy 305, maybe a 350. I like the reliability that the small blocks have, as well as the cost of parts. Currently I'm averaging about 8-11mpg on my truck. So on an average work week, driving 80 miles a day and maybe 20 miles on the weekends, I'm spending right at $500 a month in gas.
Mind you gas is not getting cheaper than $2 a gallon lol it's been going up more n more lately so, this brings concern for me. I can't afford to be driving it like this if gas hits $5 a gallon like it nearly did a few years ago.