| josborn | -- 05-11-2023 @ 5:04 AM |
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Has anyone change the gear ratio in the rear end to improve the mpg for their vehicles? I was hoping to squeeze a few more mpg out of my 1935 Slant 48 to stretch past the current 9-10 mpg. Thoughts?
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| 40 Coupe | -- 05-11-2023 @ 5:21 AM |
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Should be getting about 15-20 MPG. What engine and carburetor do you have? How does the car run? Are the exhaust pipes covered with soot? Have you removed a spark plug if so are they soot covered? The original Carb. for the 35 is the Stromberg 48. In 36 Ford went to the Stromberg 97 for slightly better mileage. The 48 is a slightly bigger Carb than the 97. Ford stamped the number of teeth for the ring and pinion under the center of the rear axle usually on the raised hump in this area. Divide the numbers shown for the ratio Such as: 9 37 = 4.11 This message was edited by 40 Coupe on 5-11-23 @ 5:26 AM
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| woodiewagon46 | -- 05-11-2023 @ 7:20 AM |
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It's simple math, MPH = RPM x Tire Diameter, divided by the Gear Ratio x 336. The lower the RPM's are, the less gas you consume and the easier it is on your engine. Gear sets are available from a number of different supply companies. You however should be getting more than 9-10 mpg from your car. As 40 points out, I would look elsewhere for your unusually poor gas milage first.
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| 51woodie | -- 05-11-2023 @ 7:43 AM |
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My stock '46 Super Deluxe, 59A runs at about 17 mpg now. I was getting around 14 mpg or so, with sooty plugs, on a carb that I had rebuilt myself a few years ago. After going through all the possible causes, I couldn't figure out why the poor mileage. I sent the carb and fuel pump off to Charlie New York for him to rebuild. He rebuilt both, and ran them on his test engine before sending them back. When I opened the box, I found a baggie with two jets in it. I called Charlie to find out about the jets, and he told me that the number on the jets were the right sizing, but at some point the jets became oversized. Also the fuel pump, which I tested at 3.5 psi, had a note on it, "2.5 psi". Thus the poor mileage and sooty plug problem was solved.
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| carcrazy | -- 05-11-2023 @ 8:42 AM |
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A higher gear ratio (lower numerically) will definitely improve your fuel economy and reduce the wear on your engine. One of the most important factors that determine your fuel economy is the type of driving the vehicle experiences. Short trips where the engine barely warms up produce much lower fuel economy than long trips where the engine is operating within its most efficient range. High speeds, above 55 MPH, also reduce fuel economy unless you have an overdrive ratio which allows you to reduce engine RPM. Other factors that reduce fuel economy are ambient temperature and altitude. Ideal conditions for maximum fuel economy would be outside temperatures between 60 and 70 degrees F and an elevation of approximately sea level.
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| wmsteed | -- 05-12-2023 @ 10:29 AM |
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You have to be very careful in trying to re-gear and/or add an overdrive with the thought that you can improve fuel mileage. The cost to re-gear a vehicle can be very high, like over $2,500. Several years ago when fuel was over $5.00 a gallon I was going to re-gear/ add an OD to one of my vehicles, the estimated cost was $2,800. I ran the numbers, based on an expected 3. mpg improvement it would have required 60 k miles of driving to break even on the modification cost. I would suggest that you follow some of the other suggestions to improve mileage in lieu of trying to reinvent the wheel. Improving the ignition, wires, plugs and coil along with re-jetting the carb and raising the operating temp with good thermostats, and improving the exhaust can do wonders to improve the mileage. If you can find a good tuneup shop that thinks modern, but leans towards vintage, they can do wonders to vintage engines with computer tuning. I had a '73 Chevy C-20 w/454 engine that was classified as a gross polluter. It failed smog tests every year. My tune up man did all of the things I mentioned in the above, adding oxygen sensors to the head pipes like modern cars have. Tuning the engine with a computer system raised the mileage from 6/7 mpg to 15/16 mpg and solved the emission problems. Bill 36 5 win delx cpe
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| josborn | -- 05-14-2023 @ 11:58 AM |
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Thank you, Bill. I appreciate your expertise and time.
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| 37RAGTOPMAN | -- 05-14-2023 @ 2:20 PM |
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Do you live in a hilly area, or flat surface. this make a big difference, in town driving,? for better milage and better highway speed go with the 354. ratio not easy but worth the trouble I did this to my 37 years ago I bought the parts from EARLY FORD V8 SALES in SC WWW.EARLYFORD.COM 1-800-417-2247 ALSO QUICK CHECKS, also make sure your choke is all the way off, no dragging brakes, tire pressure correct, HOPE this helps 37Ragtopman, Maine
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| wmsteed | -- 05-15-2023 @ 9:44 AM |
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There are several problems that can crop up when a vehicle is re-geared to a higher ratio if the average driving conditions of the vehicle is not taken into consideration.. Actually an overdrive is the best solution. An OD equipped vehicle generally has a lower gear ratio because most OD's are generally a 25% improvement, therefore the vehicle has low gears for power and higher gears for cruising. My '36 has a Columbia with 3.78 gearing. Generally the axle ratio in a '36 would be 4.11, the Columbia's were all dealer installed, so a 3.78 ratio would have been a little high. I changed the engine in my car to a 59AB that has been modified for higher HP, therefore my car has always ran very well... Bill 36 5 win delx cpe
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| flatfoot | -- 05-15-2023 @ 3:49 PM |
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My '36 Ford 4dr touring sedan gets 9 miles to a gallon. It is an overhauled '37 motor with 39 transmission and a new stromberg 97 carb. It runs very good and I drive it a lot almost everyday. I can go up I-5 65 mph. I love how it runs. I most always go 55-60 mph on the freeway, however. But the mpg is always at 9 mpg.???? It's a mystery to me. Everyone always tells me that it should get 12-15 mpg, but I have never had that good mpg. I, too, am open to suggestions. Thanks.
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| carcrazy | -- 05-15-2023 @ 9:20 PM |
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Flatfoot, What rear axle ratio do you have? If it is the 4.11:1, you could improve your fuel economy by going to a 3.78:1 or higher ratio. If your engine is running rich, you can go to smaller main metering jets in the carburetor. You can also increase your spark advance by 2 to 4 degrees or so until you get to spark knock. Once you reach spark knock, back off on the spark advance until the engine runs without knock under a load.
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