98 GT SPEEDOMETER 20 MPH TOO FAST
01-30-2011, 12:09 PM
#13
Thread Starter
Join Date: Jan 2011
Location: indiana
Posts: 7
I will figure out my ratio soon... I have not had the time yet. I don't even have to give it any gas to take off , just let the clutch out slow and it will take off smooth from an idle. I just got it last SUNDAY and so far I have completely deatailed: Exterior , interoir,engine bay and trunk. I have even changed the coolant. Next project is oil change and speedo fix.
02-02-2011, 06:38 PM
#15
1st Gear Member
Join Date: Oct 2010
Location: Texas!
Posts: 110
Tuner will not work on 96-98's
A mechanical speedo gear change will get you close but you are gonna need a speedcal to be spot on
http://www.dallasmustang.com/mustang...DED-RANGE/7626
A mechanical speedo gear change will get you close but you are gonna need a speedcal to be spot on
http://www.dallasmustang.com/mustang...DED-RANGE/7626
Exactly!
I used the speedcal and it fixed the inaccurate speedo issue for me. Fwiw, DM sells the speedcal to AM as well as other outlets...
02-02-2011, 06:40 PM
#16
4th Gear Member
Join Date: Sep 2009
Location: NC
Posts: 1,481
I'm stumped too! 2 1/4 DS rotations to 1 wheel rotation is a 2.25 ratio. Second, if you are turning 2000rpm at 55mph, it does not have stock gears in it (unless you have some really tiny tires).
If you know someone with a GPS, you can check your indicated speedometer reading against your actual speed. That will tell you the exact amount of error on your speedometer. If you do this, take your GPS reading at 30mph, 45mph, and 60mph. The GPS reading divided by the speedo reading should give you the same answer each time.
It is critical that you determine what gears you have in the rear before you do anything else.
02-02-2011, 09:43 PM
#19
4th Gear Member
Join Date: Sep 2009
Location: NC
Posts: 1,481
Those tires are about 3% less circumference than the 245-45-17's. That equates to only 2 mph difference at 60mph.
What exactly were the results from the comparison with the GPS? What did the GPS read when you were going 60mph?
Did you check it at several speeds? That would verify if you have a linear error (a percentage vs the same amount at every speed). The wrong speedo gear would give you a linear error. If the error is not linear, then you may have some other type of issue.
What exactly were the results from the comparison with the GPS? What did the GPS read when you were going 60mph?
Did you check it at several speeds? That would verify if you have a linear error (a percentage vs the same amount at every speed). The wrong speedo gear would give you a linear error. If the error is not linear, then you may have some other type of issue.
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