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Old 03-26-2014, 05:00 PM   #1
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Join Date: Jun 2013
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Triple-E MicMac IV Final Gear Ratio?

Does anyone know what the stock final gear ratio was in this unit?

It was built on a 1979/1980 B300 chassis with a 360 engine and a 727 engine.

It's roaring down the road at 80kph ... at 100kph it's screaming and up around 3000rpm. There's a hitch on the back and I wonder if someone changed the rear gear ratio at one time.

Regardless, I'm thinking of dropping it a little so the engine isn't revving so high at highway speeds, and hopefully save me a little fuel economy. It accelerates up hill like a champ, so I'm thinking it might be overgeared a bit right now.

Just looking for ways to improve fuel economy a little. I managed to improve it a bit when I found a port on the thermoquad carb hadn't been properly plugged.

I'm now running synthetic oil in the engine, and it already has dual exhaust pipes.

Thanks in advance!

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Old 03-26-2014, 06:29 PM   #2
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Location: Chicago Area
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you may be able to pick up a half mpg or so, but not much more. We find this out with our Revcons. For the front wheel drive, Revcon used a transfercase with the driveshaft running forward. The transfercase has a 1:1.11 step up gearing. Since it only takes about 2 hours and some basic tools to swap the gears, this was a common practice amongst many Revcon owners. The report was that you only lost about a 1/2 mpg by doing the swap. That put the engine at around 3K RPM at 65, similar to what you are talking about. So while you could make the change, the savings will take a long time to pay for its self. On the other hand, what is more likely is that you will still turn the same RPM, but just drive faster. Ask me how I know.

'83 Revcon Prince 31' FWD FMCA F298817
502 w/Howell/GM ECM/Edelbrock MPFI,Thorley's & Magnaflows, 4L85E 4 spd, KoniFSD
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Old 03-27-2014, 04:26 PM   #3
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To move the mass from point a to point b requires a certian amount of work.

Resistance such as wind or hills add to that work.

Fuel contains fixed amount of energy and the engine converts energy to work at a consistant rate.

Changing gear ratios changes the rpm of the motor but if it causes rpm to drop below sweet spot then the engine then works harder for same movement of mass.

Another example is many service trucks purchased by agents thinking smaller motor were puzzled by the larger motors having a lot better mpg.

Smaller motor was fine until you loaded the truck then the engine needed to have the available torque which smaller engines lacked.

Changing gear ratio causes reduction in delivery of torque to wheels so little gain in mpg on flats could be at cost of dpeed and mpg with heat gain in hills.
Tony & Lori
1989 Country Coach Savannah SE
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