Speedo calibration after gears

[J_lope82]

I’m about to swap to 3.73 gears on my manual 96 GT. I thought I could calibrate my Speedo by changing tire size with Forscan. I tried it today and I’m not getting the option to rewrite anything on my PCM. I’m guessing because it was previously custom tuned.
Does any one know if I should be able to do it with Forscan?
What are my other options for calibrating the speedo on my car?
TIA

 

[07GtS197]

You can’t change the speedo settings on the pre 99 mustangs. You’ll have to use something like an Abbot era or Dallas speedcal which are near impossible to find.

 

[apsmith49921]

Dakota digital makes an adapter as well its only 100 bucks I've considered giving it a shot. Add power, ground and split the signal and should work

 

[ttocs]

use your phones gps for speed

 

[J_lope82]

use your phones gps for speed

Yeah I have that just trying to fix it right.

 

[lwarrior1016]

Dakota digital gauge cluster will solve that issue.

 

[J_lope82]

So a hand held tuner won’t work?

 

[badass98svt]

So a hand held tuner won’t work?

Nope. Not with pre 99 Mustangs.

 

[badass98svt]

I've always used a Speedcal.

 

[Frank.JD.Perez]

Speedcal and i think you can also do that with a sct tuner. I have the speedcal on my car personally

 

[lwarrior1016]

Tuners won’t fix pre 99. It’s not ecu controlled. It’s a signal straight off the speed sensor.

 

[J_lope82]

I just saw that LMR has a calibrator for sale. The Abbott one.

 

[badass98svt]

Speedcal and i think you can also do that with a sct tuner. I have the speedcal on my car personally

SCT will only work on 99+

 

[Frank.JD.Perez]

My sct gives me the option to on my 97 though

 

[J_lope82]

Which SCT do you have?

 

[lwarrior1016]

My sct gives me the option to on my 97 though

It will give the option, but it doesn’t work. The speedometer is a signal straight from the sensor.

 

[Maximum95]

Are '96+ cars not like T5 cars? You can't change the speedometer gear? Or is '96+ stuff all digital signal...

 

[cobrajeff96]

You can change the speedo gear inside the trans. It'll get you close. Not perfect, but just about. For my application, I would up using a red (21 tooth) and it's been great. Granted, a lot has changed because of T-56 Magnum, 4.10 gears, different tire sizes since OEM form, etc.

The mid/late 90s Mustangs are electro-mechanical so you have options. The Dakota Digital SGI-100BT is another great option and one I currently use and I can't recommend it enough. It'll do both speedo and tach. But the real icing on that cake is the bluetooth smartphone app interface. You can literally watch your speedo needle change as you drive and tweak the settings on the app. So cool.

Files attached.

 

[whiplash473]

I changed the worm gear in my T-5 (purchased from LMR) and it got it close, as cobrajeff ^ said. It isn't exact but it's within one or two miles per hour.

 

[J_lope82]

I called LMR and they said the worm gear is only for pre 96.