Well guys it took a lot of searching but I've finally found a solution to all the Speedometer Calibration issues, this is more directly aimed at those who swapped in a newer 5 speed manual into their car and can't get the Magnetic reluctor wheel setup to work, however if you have an Automatic it is also beneficial. Originally our cars use the VSS gear driven assembly. With the newer transmission installed you are still using a gear, but it is not directly driven, it is using a reading based off the reluctor wheel. The issue here is our stock output shaft on the 4R70W has 7 drive teeth on it as compared to the newer transmissions and our newer 5 speeds are using the 12 tooth reluctor wheel. What this does is make our speedometers peg out to the speed limiter in 2nd gear!
Here is a further explaination : http://www.accutach.com/Pages/VSSvsOSSSwaps.aspx
The basic idea of this is that we are getting readings off a 12 tooth reluctor wheel vs a 7 tooth drive wheel. This increases our Pulses Per Mile SIGNIFICANTLY!
Here is how to get this fixed. It IS possible to convert your VSS to read the OSS signal WITHOUT a PCM module from the newer mustangs. So how do I calculate this? Well, you just have to plug in your old Pulses Per Mile based off your original driveline configuration, then calculate the Pulses Per Mile (PPM) for your new driveline configuration. Both of these can be calculated by these websites and formulas:
TIRE Rotations Per Mile (Variable#1 for the VSS PPM Calculation)
NOTE: I used this website because it tries to compensate for the weight of the vehicle on the tires to calculate the RPM instead of unmounted RPM which is significant for calculating the VSS PPM.
Formula 1: VSS PPM:
Formula 2: OSS PPM:
OSS Signal Rate = Tire Revs/Mile * Axle Ratio * OSS Reluctor Wheel Tooth Count
As you can see these two PPM's are DRASTICALLY different! Now that you've figured out your starting PPM and your final PPM you can determine the dipswitch settings for your EXTENDED RANGE DALLAS MUSTANG SPEEDCAL by plugging your results into the calculator on this website:
If you've done everything right your speedometer should be fairly accurate, if it's off by a bit you need to go back and check over your calculations and see if there is a variable you need to adjust.
I have verified this on my own personal setup and it works perfectly!
Here is an example of how I calculated my code:
My original drivetrain was setup like this
-P215/70R15 Indy 500 tires (774.6 RPM)
-1995 Stock 4R70W (7 tooth drive gear)
- 3.08 Rear Differential
-Green 17 tooth driven VSS gear
This gave me a total PPM of 7859.000, the speedometer is expecting 8,000 PPM which is a 2% error. To correct it just set your original PPM to 8,000 and plug it into the dip switch setting calculator above.
My final drivetrain is setup like this:
- 245/45R17 Dunlop Direzza DZ101 Tires (809.9 RPM)
-2008 Shelby GT TR-3650 (12 tooth reluctor wheel [Magnetic])
-3.08 Rear Differential
This gave me a total PPM of 29933.904
After plugging this into the calculator I got a dipswitch setting of : 0111011111
That dipswitch setting will eliminate the 2% error I had from the factory, and also will adjust the speedometer to work with all the modifications in my drivetrain.
NOTE: THIS WILL ONLY WORK WITH AN EXTENDED RANGE SPEEDCAL!!!