Going to look at another Stang...Question about 4:10's & Milage

huskerpower02 · Jun 15, 2004

Ok so im going to look at a new stang and the guy added 4:10's, but never corrected the speedo for it. so i was wondering how much faster a set of 4:10s add the miles on. Thanks for your help.

-Drew

stang976 · Jun 15, 2004

if it helps I had 3.55 with no calibration and it was off by 15 mph. I would be going 30 and it would say 45

SuperStang83 · Jun 15, 2004

It will throw it off quite a bit, like adding miles when it shouldn't be. I'm not sure of an exact equation though. Sorry!

94TURBO5 O · Jun 15, 2004

You will off like 15-18 mph and it also depends on the wheel size.

95WhiteVenom · Jun 15, 2004

with 3.55's and 255/45/17's I'm off by 5mph. Its best to get the speedo gear cause most cops don't understand you when you tell them about it, and the ones that do know what your talkin about don't care.

ShiftTheDrift · Jun 15, 2004

That's funny.. Sounds you're gonna go buy my last car. It was a 2001 red GT with 4.10s and being the lazy person I am, I never recalibrated the speedo. The speed will be off by 15 to 18 mph and obviously the shift points are a lot closer, takes about a day to get used to em.

89MustangGX · Jun 15, 2004

If the speedo setup is done by gears, it will be off by a percentage. So if all he did was drive around town, it will be off less than if he cruised on the highway all the time.

HazMat404 · Jun 15, 2004

89MustangGX said:
If the speedo setup is done by gears, it will be off by a percentage. So if all he did was drive around town, it will be off less than if he cruised on the highway all the time.

exactly what he said. you will never ever be off by a set amount. i have a speedo gear for a 3.73 with my 4.10 in my car. someone did the math for me with my tire size and blah blah and im off by right around .914 compared to just .909756 (due to the 3.73 gear divided by the 4.10 that is actually back there). so pretty much im off 10% so every 10mph im going, my speedo reads 1mph faster. im very used to it by now and my tweecer r/t verified that this calculation is correct down to 1mph (due to a lil more than .9).

summary: you will be off by a % that can be figured out pretty easily if you want just an idea of how off you are

94TURBO5 O · Jun 15, 2004

Get a SpeedCal and that will solve it.

5.0_GT_kid · Jun 15, 2004

Do you still have the other stang, drew?

huskerpower02 · Jun 15, 2004

5.0_GT_kid said:
Do you still have the other stang, drew?

ya i do......and still for sale

and on a side note, i wasnt talking about how bad it would knock off the speedo, we have enough of those posts already, i was walking about how quickly it would add false miles to the odometer.

89MustangGX · Jun 15, 2004

huskerpower02 said:
and on a side note, i wasnt talking about how bad it would knock off the speedo, we have enough of those posts already, i was walking about how quickly it would add false miles to the odometer.

I answered that -- see my post above.

huskerpower02 · Jun 15, 2004

89MustangGX said:
I answered that -- see my post above.

yup

5.0_GT_kid · Jun 15, 2004

89MustangGX said:
If the speedo setup is done by gears, it will be off by a percentage. So if all he did was drive around town, it will be off less than if he cruised on the highway all the time.

Wouldn't the percentage be the same for speedo and odometer?

Common sense tells me if the speedo is off by let's say...15%..then the odometer should be off by 15% too.

So let's say he had the gears put in at 40k miles and the car now has 50k miles, then 15% of 10k should be "false mileage"

That's just what my gut tells me. I dunno though.

:OT: Drew, how much you asking for the stang, and why are you selling it, if you don't mind my asking. That's a good looking car.

89MustangGX · Jun 15, 2004

5.0_GT_kid said:
Wouldn't the percentage be the same for speedo and odometer?

Common sense tells me if the speedo is off by let's say...15%..then the odometer should be off by 15% too.

So let's say he had the gears put in at 40k miles and the car now has 50k miles, then 15% of 10k should be "false mileage"

That's just what my gut tells me. I dunno though.

You know, I think you're right -- I was lost in my own logic.

Using the 15% figure -- If he drives for 100 miles at 50MPH, he will add an additional 7.5 miles per hour he drives, or a total of 15 miles extra. If he drives the same 100 miles at 100MPH he will add an additional 15 miles per hour he drives, or 15 miles total. The speed does not matter, it's a percentage -- which was my original thought until I veered away from it with my highway and town statement.

Good thinking.

5.0_GT_kid · Jun 15, 2004

Yeah cuz I was like "doesn't the wheel turn so many times per mile no matter the speed?"

Either way you were still right. Nice car btw I saw your CarDomain site

HazMat404 · Jun 15, 2004

yeah, ur completley right. when i get my mpg i just take what it says on my odometer (trip is busted) and multiply by my gallons used then multiply by the .91 (or just knock off about 10% in my case which is easier) and i get my mpg. i thought i used to get 18mph then i found all this out and now i know i only get about 16.4-5ish. that percentage is gonna involve anything related to the spinning of the wheels (mph, odometer, tripometer). i know ive chaulked up a good 2-3 thousand extra miles since i did my 4.10 about 2 years ago. not a huge deal but to some it might be.

a speedcal will solve it all but it was like $250 installed when i wanted my gear done. didnt have that cash lyin around. i would if i did have the money tho

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