The Ford Barn

Chris Haynes · 02-17-2018, 11:41 PM

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?

BILL WILLIAMSON · 02-18-2018, 08:21 AM

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

jhowes · 02-18-2018, 11:11 AM

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

Charlie Stephens · 02-18-2018, 11:35 AM

Quote:

Originally Posted by Chris Haynes

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?

Unless you are doing something out of the box why not just buy a new gear and turtle? What are you doing?

Charlie Stephens

Bob C · 02-18-2018, 11:45 AM

Just do a search for SPEEDOMETER RATIO ADAPTER, there all over the place.
There are almost 100 listed on Epay.

Bob

duke36 · 02-18-2018, 01:27 PM

Sponsored Links (Register now to hide all advertisements)

Go to PATC (performance auto transmission center.com) and select ratio needed. For example if 3 or 4mph fast or slow, they can help calculate the ratio needed and what cable end adapter may be needed.

Y-Blockhead · 02-18-2018, 03:54 PM

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!

Synchro909 · 02-18-2018, 04:14 PM

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.

Ruth · 02-18-2018, 04:50 PM

Quote:

Originally Posted by Synchro909

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.

I don't understand. If I change the drive gear so my speedo reads correctly, how can the odo be off? Please explain.

Mark in MT · 02-18-2018, 06:06 PM

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

Charlie Stephens · 02-18-2018, 09:52 PM

Quote:

Originally Posted by Synchro909

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.

You are correct. I was assuming that he had somehow had the wrong gear. Best place to start would be to check the odometer.

Charlie Stephens

Synchro909 · 02-18-2018, 10:01 PM

Quote:

Originally Posted by Charlie Stephens

You are correct. I was assuming that he had somehow had the wrong gear. Best place to start would be to check the odometer.

Charlie Stephens

I only sound like I know all about it because I have just been down this road myself ad found out the hard way.

Chris Haynes · 02-18-2018, 11:37 PM

Quote:

Originally Posted by Charlie Stephens

Unless you are doing something out of the box why not just buy a new gear and turtle? What are you doing?

Charlie Stephens

I have oversized tires.

Synchro909 · 02-19-2018, 01:46 AM

Quote:

Originally Posted by Chris Haynes

I have oversized tires.

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.

bettlesr · 02-20-2018, 11:23 AM

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

02-17-2018, 11:41 PM	#1
Chris Haynes Senior Member Join Date: May 2010 Location: Camarillo, CA and Pine Grove, CA Posts: 2,832	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? __________________ 1921 Runabout 1930 Tudor Early 1930 AA Speed costs money. How fast do you want to go?

02-18-2018, 08:21 AM	#2
BILL WILLIAMSON Senior Member Join Date: Dec 2010 Location: FRESNO, CA Posts: 12,560	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 __________________ "THE ASSISTANT GURU OF STUFF"

02-18-2018, 11:11 AM	#3
jhowes Senior Member Join Date: Jul 2010 Location: upstate NY near Mass border Posts: 789	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

02-18-2018, 11:45 AM	#5
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 8,743	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
duke36 Senior Member Join Date: Jun 2015 Posts: 1,414	Re: speedometer drive ratio adapter Sponsored Links (Register now to hide all advertisements) Go to PATC (performance auto transmission center.com) and select ratio needed. For example if 3 or 4mph fast or slow, they can help calculate the ratio needed and what cable end adapter may be needed.

02-18-2018, 03:54 PM	#7
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 5,848	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!

02-18-2018, 04:14 PM	#8
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 7,496	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. __________________ I'm part of the only ever generation with an analogue childhood and a digital adulthood.

02-18-2018, 06:06 PM	#10
Mark in MT Senior Member Join Date: May 2010 Location: Western MT Posts: 218	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 __________________ Mark in MT Always looking for another opportunity to be wrong.

02-20-2018, 11:23 AM	#15
bettlesr Senior Member Join Date: Nov 2010 Location: Florham Park, NJ Posts: 396	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 __________________ 1965 Lotus Elan S2 1930 Model A Sport Coupe Last edited by bettlesr; 02-20-2018 at 11:34 AM.