Gear Ratios: Misinformation at its worst.

Discussion in 'Experienced Truckers' Advice' started by Hammer166, Apr 28, 2021.

  1. Hammer166

    Hammer166 Crusty Information Officer

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    And hope for a slight downgrade!
     
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  3. Russian Rabbit

    Russian Rabbit Road Train Member

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    i apologize, but i use term "lower" gear to mean 4.11, 4.56, 4.88 etc.

    "higher" gear to mean 3.08, 2.56 etc.

    i'll try to be more clear next time....
     
  4. RStewart

    RStewart Road Train Member

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    Yeah I would have to slow to 55 to run direct. I use a scan gauge while I'm driving and I noticed that when I run in direct boost has a much bigger impact on fuel mileage than it does in overdrive. Basically, in OD I can use 6 lbs of boost and my MPGs will show just under 8.5 mpg but in direct that same 6 lbs of boost shows a little over 6 mpg. IDK... I just run it in 12th unless i want to run 70 mph+ and keep the cruise control turned off and MPGs improved over running 65 mph in 13th which is about 1300 RPMs. Motor doesn't seem to regen as much either.

    You are correct, lower gears is a higher number, higher gears is a lower number.
     
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  5. RStewart

    RStewart Road Train Member

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    ok, but only in the calculator. lol
     
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  6. God prefers Diesels

    God prefers Diesels Road Train Member

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    That's how 99.999999999999% of the world does it.
     
  7. Rideandrepair

    Rideandrepair Road Train Member

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    I fully understand now, no wonder the terminology gets so mixed up. Higher is lower etc. Lol. So, a 3.55 for example turns the ring gear 3.55 times for each single revolution of the pinion gear.......... Roughly the same with a 3.54. Regardless of actual number of teeth, same end results. The key is the term ratio! Should have been obvious, I guess. Think I got it now!! If not, don’t give up on me. I’m a little slow at times. But eventually learn.
     
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  8. Rideandrepair

    Rideandrepair Road Train Member

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    I don’t know about that. Seems I’ve heard a lot of talk about taking a 3.23 out and putting a higher 4.10 or 4.56 but not a 4.88 that’s too high!!! I guess that’s why I’ve always had it backwards in my understanding.
     
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  9. Brettj3876

    Brettj3876 Road Train Member

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    Keeping it out of the boost as much as possible. 90% of the time im in 12th around 1600-1650. That will get me better mpg vs 13th at 1400 because I'm only 7-8psi vs 15-20 trying to maintain speed at 1400 with a load on
     
  10. RStewart

    RStewart Road Train Member

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    That's been my experience as well. RPMs doesn't hurt MPGs by itself.
     
  11. Rideandrepair

    Rideandrepair Road Train Member

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    I can’t help but think of my friends 72 Gremlin, 258 6 cyl 3 speed. It was a 304 strip car with a 4.88 gear. He got it for free from a family friend. Had a big slit in the floor from flywheel coming off, the previous Owners lucky he didn’t lose half his leg. Never got the 304, or 4 speed. Only the original 6 cyl. It had Very low miles, a General Kinetics performance cam. He put it together, painted the engine hemi orange. It would spin big M50 tires. Lol. Tore up the clutch in no time. Put a Warlock HD clutch. It was a blast to drive. Burn 1st, second, and squawk third. Once it hit 50 mph, it was done. It looked like a roller skate, white with black racing stripes. Had a lot of fun in that car as a teenager. Red light to red light, it was crazy quick. They’d always ask, what’s in it? 6 cyl!! Lol. Often had to pull over and pop the hood for proof. He had plans for a small 4 bbl and header, but wrecked it one day on his way to pick me up from work.
     
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