foxtrot

I have the cable type of speedometer in my 1998, I guess the cut off was 1998 as the 1999 speedo is electronic and can be corrected using a chip. Changed rear gears and the 4:10 is way off. Wondering if it will throw anything else off??

Question:

For a 1998 cable speedo set up and manual trans what is the speed information used for in the ECU?

I am betting nothing.

TXMach

If the speedo is off so is the odo. I don't think it throws anything else off. You'll need a speedo gear.

http://search.americanmuscle.com/sea...=mustangtuning

foxtrot

Yes I have the 23 tooth speedo gear for the 4:10 in it right now but the speedometer readings are still off. It shows I am going 10-20 MPH faster than I am really going. And yes I am racking up miles that are not real.

The question was if the speed is not right does it matter to the engine ECU/IAC control etc? The car runs really good after all the work I put in it. Actually better than when I first purchased the car. So I am guessing that its not inputting any signal not the ECU. Would just be noce to know for sure.

TXMach

I wish I had an answer for you. Anyone else wanna chime in?

LilRoush

What size tires are you running?