Speedo problems...need help please. - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 3 Old 03-20-2008, 05:25 PM Thread Starter
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Question Speedo problems...need help please.

My stock rearend broke, so I replaced it with an 04 Mach 1 rearend. I know the gearing is different than what used to be in there and my options are basically to either buy an electronic speed recalibrator, or use a reprogrammer to modify my ECU. Rather than pop $100 for the recal box, one of my friends has a Diablo Predator Tuner so I used that. It is the right model number for my car, and I reset it before using it so I tuned my car with the stock tune.

No matter what gearing I enter into it, my speedo just won't go back to normal; it either says I'm going to fast or too slow. I even tried changing the tire diameter according to the formula on Diablo's website and still nothing.

BTW, I have a manual tranny (T-5) and I believe my gears were 3.08 stock and now are 3.27's.

Can someone help me out please? Thanks...

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post #2 of 3 Old 03-22-2008, 02:16 PM
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Actually, depending on year, your stock rear was either a 2.73 (94-98 3.8) or 3.27 (99-04 3.8). All mach 1s have a 3.55 ratio.

Hope that helps

2002 Mineral grey GT 5 speed. Flowmaster 40's catback, Mach 1 grille delete, timing advance, push button starter, Bullitt pedals, FR500 steering wheel, K&N FIPK, Self ported upper intake w/ spacer, Pioneer Avic D3, MGW shifter, MM FL subframe connectors, Mach 1 springs, Bilstein HD struts/springs
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post #3 of 3 Old 04-09-2008, 02:19 PM
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I have a electronic speed recalibrator box in my garage I am not useing make me a offer.

2007 Mustang ( wifes car)
2014 F150 ( daily driver )
1998 Mustang 11.53 114mph pro charged 3.8
1989 Mustang 10.82 124mph ( sons car )
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