i think my mhp is incorrect

bboylobo · Aug 5, 2008

I was cruising behind my friends modded gtp and we gunned it down the highway. my ODOM gotup to about 150 and i thought that we were going that fast. i spoke with him about it and he said that he only got up to 130. Sometimes when im driving i get the feeling that im going slower than what my odom is telling. my thought is that the guy who owned it before me probably put 373 gears but didnt replace the speedo. is there anyway to diagnose this issue?

i just bought the car 2 weeks ago btw. its an 01 gt

RedDaemon · Aug 5, 2008

is it an automatic or manual?

fst100 · Aug 5, 2008

its the manual tranny. im the guy in the grand prix btw
i did a few searches and is this the only way to tell if the previous owner(s) swapped from the 3.27 to a 3.73 or even 4.10 gearing?

stock gearing ratio on 99-04 GTs is 3.27:1 that is the relationship between the rear wheels and driveshaft. so for every 1 rotation of the rear wheels, the driveshaft will spin 3.27 times. so changing your gears for, say, 4.10:1 means that for every revolution of your rear wheels, your driveshaft will rotate 4.10 times, thus increasing acceleration. also, as you may know, torque is spinning or revolving power, so more spinning of the rear wheels means more torque, although its not able to be measured. ...

Stark77 · Aug 5, 2008

If it's an automatic - check your engine RPM with O/D off at 50mph. If it is sitting at 2500RPM at 50mph you have 3.73's

fst100 · Aug 5, 2008

its manual

RedDaemon · Aug 5, 2008

the driveshaft/rear wheels will be the easiest way to tell. as was mentioned earlier

you can also ride next to someone else both doing "50mph". if theyre not going the same speeds, record what RPM the car is turning and report back to us. there are charts that people have that can tell you what gears you have

fst100 · Aug 5, 2008

good to know, thanks. im certain bboylobo will check back here soon ^_^

bboylobo · Aug 5, 2008

thanks guys i will check on this when i get on the road i have been working all day out in my plant so i couldnt respond.

bboylobo · Aug 10, 2008

ok here is something. sorry it took so long i just got back from vacation. when my odom says im doin 70 im actually doing 60. is this enough to tell me if i have 373 or 410? or is something just broken lol.

Mustang5L5 · Aug 10, 2008

What size tires do you have?

PS. Odometere tells you how many miles are the car. Speedometer tells you your speed.

You really need to jack the rear up and count tire rotations to tell what gears you have. Then you'll need a speedcal to recal the speedometer.

It happens a lot where guys NEED a set of rear end gears...but then take the cheap way out and don't do it right to get the speedometer reading correctly.

Stan Weiss · Aug 10, 2008

First we need to know the size of your rear tires verses the stock size. By calculations a stock '00 is doing 69.77 MPH @ 2000 RPM with 245-45-17 tires and 3.27:1 rear. It is doing 61.17 MPH @ 2000 RPM with 245-45-17 tires and 3.73:1 rear.

COramprat · Aug 10, 2008

Try this.

http://www.corral.net/tech/gearcalc.html

At 70 in 5th I'm at 2500 rpms with 4.10's.

bboylobo · Aug 10, 2008

thanks guys i just did the math and found that i have 3.73s. the guy who owned the stang before me must not have installed the calibrator or speedo to compensate for the gear change. guess im off to buy the solution

trinity_gt · Aug 11, 2008

Stock gears were 3.27. If you're out 20MPH at 130MPH, you're seeing approximately 15.4% error in speed. 3.73s would produce a 14% high-error. 3.90s would produce a 19.2% error so it does look like you've got 3.73s in there.

Sucks that not only is your speedo off but you've also been racking up 14% too many odometer miles too...

RedDaemon · Aug 11, 2008

bboylobo said:
thanks guys i just did the math and found that i have 3.73s. the guy who owned the stang before me must not have installed the calibrator or speedo to compensate for the gear change. guess im off to buy the solution

its possible the previous owner installed one of those speed cal devices from dallas mustangs or whatever it is.

this: Interior - Speed-cal, 94-2004, 5 Spd, Extended Range - Early Model Classic Mustang Restoration Parts

those things are pieces of ****

get a handheld tuner like an xcal2.

COramprat · Aug 11, 2008

-=NightHawk=- said:
its possible the previous owner installed one of those speed cal devices from dallas mustangs or whatever it is.

this: Interior - Speed-cal, 94-2004, 5 Spd, Extended Range - Early Model Classic Mustang Restoration Parts

those things are pieces of ****

get a handheld tuner like an xcal2.

Why do you say that? I've had mine for 4 years with zero issues.

RedDaemon · Aug 11, 2008

sorry, i forgot i posted in this thread.

i say that because around the time i was considering grears, folks on here and my research that i did around the internets didnt look highly upon DM or the SpeedCal itself.

theres no other reason why i think theyre crap. however ive been going by info that was passed on to me here

so i could be a tool for going with what other say, and i know that. but i trusted their suggestion...not 100%, but enough to where the probability where id have a problem was too great to consider pursuing that path further (the SpeedCal)

i think my mhp is incorrect

bboylobo

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RedDaemon

fst100

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Stark77

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fst100

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RedDaemon

fst100

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Mustang5L5

That is…until I whipped out my Bissell

Stan Weiss

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...I can take it. I think.

bboylobo

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...I can take it. I think.

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