I just got new wheels/tires that are a slightly different height than stock, I don't know if my speedometer will be off (haven't tried it with GPS yet) but if it is, and I buy the speed cal for 94-04 manual mustangs, will it still work if I swap in a new tranny and 4.6l V8 and 8.8" rear diff?

 

Speedcal only changes for new gear ratios, not for tire height changes.

 

Untrue...I have a speedcal in my gt and one in my fiance's v6. The v6 has my old 20" rims on it, and without the speedcal, the speedo read ~5-6 mph slower than actual speed. It still has stock gearing and with the speedcal, it is dead on. I got mine from Dallas Mustang, and they have a calculator online where you put in your specs for wheel size, tire size, and gears and it will give you the 10 digit code for the toggle switches within the unit that will dial in your speedo exactly. Works like a charm.

Scott

 

Well i'll be damned...looks like someone in the office is getting a smack upside the head for bad info.

 

When did I say I wanted to sell it as a GT? When did I even say I wanted to sell it at all? I plan on keeping this car for a very long time. And actually it is cheaper for me to swap engines than to buy a GT because of insurance.

Thanks everyone else for answering my question.