Custom Ratio Adapter, Speed Up or Slow Down your Speedometer, Call 1-888-201-2066

Custom Ratio Adapter

Custom Ratio Adapter.

Speed Up or Slow Down your Speedometer with a custom built ratio percentage.

For assistance call Jim @ 1-888-201-2066!

The male side can be turned 180 degrees, just remove the 4 screws and flip one side to make it offset.

This adapter is only used at the transmission or at the transfer case, not behind the speedometer head.

Unfortunately we cannot refund special orders, but we can rebuild your adapter for a rebuild fee!

So if your new percentage is not working out for you, give Jim a call!


CLICK HERE for our Main Speedometer page!

* Electronic Ratio Adapter (ERA), to adjust electronic speedometers

Electronic Ratio Adapter (ERA), to adjust electronic speedometers

Electronic Ratio Adapter (ERA), to adjust electronic speedometers

Now You Have the Solution to Your Speedometer Problems….. For 700R4, 4L60E and others with electronic speedometers.

# 69. Any change in a vehicle’s tire size or rear axle ratio will cause the speedometer reading to be inaccurate. The Electronic Ratio Adapter (ERA) is designed to correct this problem. With the ERA, you simply hook up four wires, set the DIP switches according to the calibration table included with your order, and you are ready to go. What does the Electronic Ratio Adapter do? The automotive industry has a great variety of part sizes, types, shapes and descriptions, but regardless of make, model or year, a few things are standard. One of those standards has been the number of revolutions a speedometer cable will make for each mile traveled. Nowadays, electronic pulses have replaced the rotating cable, but the same principle applies. The Pulse Ratio (the number of pulses per mile traveled) remains the same, regardless of speed, since the same distance is traveled and the same number of pulses have occurred each mile no matter what the speed was during that mile. However, this Pulse Ratio can be made to vary from the true when modifications are made which change the number of electronic pulses per mile on a particular vehicle. This is most commonly caused by changing the tire size (increasing the outside diameter of the tires will cause the tire to travel further before making a complete revolution), but other modifications could have the same result. When the Pulse Ratio is thrown off, the speedometer/odometer will be inaccurate and corrections must be made. This relative difference between true speed and the speed indicated on the speedometer is called the Variance Ratio, and it is corrected using the Electronic Ratio Adapter.

Wiring Diagram of Electronic Ratio Adapter:

Electronic Ratio Adapter

 (Red Wire) 12 volts, ignition on
 (Black Wire) Ground
 (White Wire) Signal in from the speed sensor
 (Blue Wire) Signal out to the ECM / Speedometer

Currently the Electronic Ratio Adapter is not recommended for 2000 and newer Fords and 2001 on Dodge Rams.

Main Speedometer Gear Page CLICK HERE


* Ford speedometer ratio adapter, Number 55RA.

Ford to Gm type cable ratio adapter

Ford Speedometer Ratio Adapter

# 55RA. Ford speedometer ratio adapter. Must be used with screw on cable top and bottom. Comes in minus 15%, minus 28% or plus 44%. These units are specific to Ford mechanical cable transmissions and transfer cases and do not go behind the speedometer head.


 

PG1. Early Powerglide / 3 Speed Standard Speedometer Driven Gears

Early Powerglide / 3 Speed Standard Speedometer Driven Gears

 PG1. Early Powerglide / 3 Speed Standard Speedometer Driven Gears. Comes in 20, 21, 22, 24 and 25 tooth. The 20 and 21 tooth Powerglide gears have a .785″ diameter head and the 22, 24 and 25 tooth three speed standard gear has a .865″ diameter head. The overall length runs 2.890″ to 2.900″. Also fit some other early GM automatic transmissions. If your speedometer is still off with one of these gears installed it can be corrected with a ratio adapter.


 

E-Z SQUEEZE UNIVERSAL FRONT PUMP AND SPEEDOMETER GEAR PULLER

E-Z SQUEEZE UNIVERSAL FROUNT PUMP AND SPEEDOMETER GEAR PULLER

Features:

  • Heavy duty all metal construction
  • Removes pumps by using a removable knob
  • Removes speedometer gears with 5/8″ end wrench
  • New style adapter fits many front pumps
  • Removes plastic and steel speedometer gears
  • *CAUTION: DO NOT USE THIS TOOL WITH IMPACT TOOLS

 

Transmission grouping:

  • 250, 250-C, 350, 350C3
  • 375,400(3L80),425,475(3L80-HD)
  • POWERGLIDE

 

* Speedometer Gear Calculator *

Speedometer Gear Calculator, Speedometer Gear Calculator

*Speedometer Gear Calculator*

 

Main Speedometer Page: Click Here

To determine your tires true diameter in relation to determining what speedometer gears you need, measure from the ground up to the center of the axle then multiply by two. The actual run out of the tire can be as much as 2 to 3 inches less than what the circumference of the tire measures. In effect your tire has two diameters.

To determine your rear end ratio, raise both tires off of the ground, turn both tires at the same time one complete turn, at the same time count the turns of the drive shaft, this is your ratio.

Speedometer Calibration:
Variables such as the vehicle’s axle ratio and tire diameter affect the accuracy of the speedometer. The following speedometer drive gears and driven gears are available for the 700R4 / 4L60 transmissions. Most cars and trucks with low rear end ratios will take a 15 tooth drive gear. There are two driven gear housings, one for 34 through 39 tooth driven gears and one for 40 through 45 tooth driven gears. Look at the bottom of the speedometer face for the numbers 940, 960, 1000, or 1020. These numbers are the number of revolutions the speedometer cable must turn in one mile of travel. Your speedometer may or may not show a number. Most speedometer from 1965 on use 1000.

Twelve speedometer driven gears are available for the 700R4 / 4L60 transmissions to calibrate the speedometer with various axle ratios and tire diameters. The number on the driven gear housing must match the number of teeth on the driven gear. Unless driven gears with more than 45 teeth and / or drive gears with fewer than 15 teeth become available, it will be impossible without using a ratio adapter to have an accurate speedometer with rear end gear ratios lower (higher numerically) than 4.10:1, unless 27 inch or larger tires are installed.

700R4 With 15 Tooth Drive Gear

Axle Ratio Tire Height Driven Gear Teeth
4.56 33 42
4.56 35 39
4.10 26 45 will work, but will read about 3 MPH fast at 50 MPH.
4.10 27 45
4.10 28 44
4.10 29 43
4.10 30 41
4.10 31 40
4.10 33 38
4.10 35 35
3.73 26 43
3.73 27 42
3.73 27 1/2 41
3.73 28 40
3.73 29 39
3.73 30 38
3.73 31 36
700R4 With 17 Tooth Drive Gear
Axle Ratio Tire Height Driven Gear Teeth
3.73 28 45
3.73 29 44
3.42 26 45
3.42 26 1/2 44
3.42 27 43
3.42 28 42
700R4 With 18 Tooth Drive Gear
Axle Ratio Tire Height Driven Gear Teeth
3.23 26 45
3.23 26 1/2 44
3.23 27 43
3.23 28 42

700R4 / TH400 / 208 Transfer Case, Speedometer Driven Gear

Speedometer Gears from Speedometer World / Speedometer Cables / Speedometer Housings

#54XX. 700R4 Speedometer Driven Gear. 

700R4 / TH400 Speedometer Driven Gears, come in 34 to 45 tooth. (Also fits 208 transfer case).

Speedometer Gear Calculator Click Here

Speedometer Calibration Variables such as the vehicle’s axle ratio and tire diameter affect the accuracy of the speedometer. The following speedometer drive gears and driven gears are available for the 700R4 / 4L60 transmissions. Most cars and trucks with low rear end ratios will take a 15 tooth drive gear. There are two driven gear housings, one for 34 through 39 tooth driven gears and one for 40 through 45 tooth driven gears.
Look at the bottom of the speedometer face for the numbers 940, 960, 1000, or 1020. These numbers are the number of revolutions the speedometer cable must turn in one mile of travel. Your speedometer may or may not show a number. Most speedometer from 1965 on use 1000.

Twelve speedometer driven gears are available for the 700R4 / 4L60 transmissions to calibrate the speedometer with various axle ratios and tire diameters. The number on the driven gear housing must match the number of teeth on the driven gear. Unless driven gears with more than 45 teeth and / or drive gears with fewer than 15 teeth become available, it will be impossible without using a ratio adapter to have an accurate speedometer with rear end gear ratios lower (higher numerically) than 4.10:1, unless 27 inch or larger tires are installed.

To determine your rear end ratio, raise both tires off of the ground, turn both tires at the same time one complete turn, at the same time count the turns of the drive shaft, this is your ratio.