TEXASx2000xMUSTANGx

so i ordered a tuner and gears, and had the tune custom for the 3.73's, but turns out my brother never got em installed and just told me he did, real nice huh :P but anyways, is it bad for me to be running stock gears witht hat specific tune? just wonderin.
thanks ahead!

0949er

your speedo will be a little off if it is set for 3.73 gears and you are running stock.

Dunno how much it is off by.

TEXASx2000xMUSTANGx

okay cool, thats it though? just makin sure, im new to all this. haha

grogan

i think your speedo is gonna be 4-5 mph off but in the sense that if your going 40 on the dash its really 45-46

i believe its 2-3 mph per gear set. 3.27 stock, 3.55 2mph off 3.7.3 5 mph off 4.10 8mph off etc.

cliffyk

It will read 87.6% (3.27/3.73) of your actual speed, so:

if it reads 40, you will be traveling 45.6; 40 * (3.73/3.27);

if it reads 50, you will be traveling 57.0;

if it reads 60, you will be traveling 68.4;

if it reads 70, you will be traveling 79.8;

if it reads 80, you will be traveling 91.3;

etc...

TEXASx2000xMUSTANGx

but no harm done though right? thats all i wanna make sure of, but thanks for all that info!

Drag5.0mustang

Nope totally fine! just the speedo will be off.

MU71L4710N

speedo off, and you actually accumulate less miles on your car than your actually driving.

im not doing the percentage math but basically, if you drive 100 miles, your odometer actually only picks up like 95 of those miles since you are really traveling faster than your car thinks.

StriderTacticaL

^^ Is that actually true? In terms of your odo being off if you don't calibrate your speedo properly according to your gear ratio?

And to the OP, why don't you just tune be readjusted so the speedo will be fixed for your stock gears?

swarthyfellow

If you go up in gear ratio you car thinks its going faster then it is. So 65 mile/h is (3.27/3.73)65 mile/h= 56.9 miles/h, time cancels and you end up with 65 miles on the tach and 56.9 actually miles. If you map your route every time you go out you should see the 87% in your tach miles and trip miles every time. Its really annoying to have to account for this in mpg and in maintenances checks like oil and trans. You should be able to get it fix with a tuner, previous to 98 have to change the trans sensor gear to adjust for it; needless to say i have not adjusted mine and i have been watching it and its usually 10% (275-45-17 rear tire). I have been doing it long enough to know when my rear tires are worth and then a smaller diameter and change 1-1.5% percent over the lifespan of the tire.