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02-17-2018, 11:41 PM | #1 |
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speedometer drive ratio adapter
Years ago my local speedometer shop, sadly now gone, sold transmissions that mounted between the drive and the speedometer cable to make the speedometer read right after you had changed rear end ratios. Does anyone have a source for these today?
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1921 Runabout 1930 Tudor Early 1930 AA Speed costs money. How fast do you want to go? |
02-18-2018, 08:21 AM | #2 |
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Re: speedometer drive ratio adapter
Good morning, Chris,
Call a TRUCK Repair Shop & ask who does their SPEEDO/TACH repair. Those types of boxes are often used on trucks. Bill Barelyawake
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02-18-2018, 11:11 AM | #3 |
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Re: speedometer drive ratio adapter
Also check sports car clubs. They use adjustable ones to make their speedo more accurate for events that the run requires accurate mileage and speed indicators. Jack
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02-18-2018, 11:35 AM | #4 | |
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Re: speedometer drive ratio adapter
Quote:
Charlie Stephens |
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02-18-2018, 11:45 AM | #5 |
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Re: speedometer drive ratio adapter
Just do a search for SPEEDOMETER RATIO ADAPTER, there all over the place.
There are almost 100 listed on Epay. Bob |
02-18-2018, 01:27 PM | #6 |
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Re: speedometer drive ratio adapter
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02-18-2018, 03:54 PM | #7 |
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Re: speedometer drive ratio adapter
Check with Gene at Flat-o Adapters http://flat-o.com/accessories/speedcable.htm I got one from him years ago for my '55 Ranchwagon when I installed a C-4 and Gear Vendors O/D behind the 312" Y-Block... Works perfect!
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02-18-2018, 04:14 PM | #8 |
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Re: speedometer drive ratio adapter
Changing the drive gears will throw your odometer off. Speedos are adjustable so why not have it adjusted to allow for the change? Papanick (who frequents the Swap Meet here) might be the guy to see.
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02-18-2018, 04:50 PM | #9 |
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Re: speedometer drive ratio adapter
I don't understand. If I change the drive gear so my speedo reads correctly, how can the odo be off? Please explain.
Last edited by Ruth; 02-18-2018 at 06:55 PM. |
02-18-2018, 06:06 PM | #10 |
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Re: speedometer drive ratio adapter
The odometer reads 1 mile for every 1000 revs of the cable. Drive the car along a road with mile posts for several miles, noting the gain or loss of the odometer. If the speed portion of the unit is in calibration, then the error should be the same amount and in the same direction as the odometer. You need to adjust the ratio of the cable drive to correct the odometer, then have the speedometer calibrated on a machine to correct it. Changing the gear one tooth on the drive on the torque tube changes the calibration 5-6%.
I have done special calibrations where the customer asked me to adjust the speedometer + or - a certain percent and did not care what the odometer reads. Mark
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02-18-2018, 09:52 PM | #11 | |
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Re: speedometer drive ratio adapter
Quote:
Charlie Stephens |
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02-18-2018, 10:01 PM | #12 |
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Re: speedometer drive ratio adapter
I only sound like I know all about it because I have just been down this road myself ad found out the hard way.
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02-18-2018, 11:37 PM | #13 |
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Re: speedometer drive ratio adapter
I have oversized tires.
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1921 Runabout 1930 Tudor Early 1930 AA Speed costs money. How fast do you want to go? |
02-19-2018, 01:46 AM | #14 |
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Re: speedometer drive ratio adapter
In that case, changing the gear is OK. You have changed both the speedometer and the odometer by doing that so changing the gear by one tooth less will be about right.
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02-20-2018, 11:23 AM | #15 |
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Re: speedometer drive ratio adapter
I got mine from Clark Brothers Instruments
56680 Mound Rd Shelby Township, MI 48316 USA Tel: 586-781-7000 Fax:586-781-7005 Email: [email protected] http://clarkbrothers.net/ratio_adapters.html
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1965 Lotus Elan S2 1930 Model A Sport Coupe Last edited by bettlesr; 02-20-2018 at 11:34 AM. |
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