I let someone borrow my superchips tuner and I'll be getting it back next week, but I want to do the install on my new gears this weekend. Does anyone know how much my speedometer be off with 3.90 gears?
How much will my speedometer be off installing my 3.90 gears?
- Thread starter Seraphitia102
- Start date
Cobra Jay
Member
It's going to be off quite a bit. Not only will your speedo be off, your odometer will be off as well. When I went to 4.10s, I didn't install my Speed Cal right away and my odometer was off about 3-4 10ths a mile.
So will it be off like to the point where for example, if i'm driving at 30mph, will my speedo read 50mph?
langod
New Member
It should read roughly 20% high.
40mph actual = 48mph displayed
60mph = 72
75 mph = 90
And your odometer wil be clicking over 20% faster -- if you drive 50 miles, your odometer will say you went 60.
40mph actual = 48mph displayed
60mph = 72
75 mph = 90
And your odometer wil be clicking over 20% faster -- if you drive 50 miles, your odometer will say you went 60.
hognutz
New Member
it will be like 10mph or so. it kind of varies based on speed and gear since it is rpm related.
short story long you will not want to do it as it will add extra milage to you car.
you can go to a gear calculator and figure you speed based on rpm.
for example 70mph with with 3.90's is 2400rpm where 70 is 2000 rpm with 3.23. that is in 5th. so you can figure you speed out based on the tach. the problem is you odometer is going to be off and off in a direction that depriciates you car faster. it is worth the money to fix it. I bought a used diablo for $250 on ebay. you can have you computer reflashed just for gears for like $100 though.
short story long you will not want to do it as it will add extra milage to you car.
you can go to a gear calculator and figure you speed based on rpm.
for example 70mph with with 3.90's is 2400rpm where 70 is 2000 rpm with 3.23. that is in 5th. so you can figure you speed out based on the tach. the problem is you odometer is going to be off and off in a direction that depriciates you car faster. it is worth the money to fix it. I bought a used diablo for $250 on ebay. you can have you computer reflashed just for gears for like $100 though.
jeffnoel
Founding Member
Good luck with those 3.90's especially if you got Motive's. I am having a hell of a time with mine, I wish i would have just got FRPP and picked either 3.73 or 4.10's. My first set whined like mad and i got them replaced through motive. We chalked up the first set to a bad install by some performance shop, but not positive and it was never proved. I got the second set installed by a different person and they are even louder. Now i know there are people on here that have them and it worked out perfect, but if your luck sucks like mine, prepare to have a nightmare of a time. I know people will say gears are gears and its all in the install, but i am now a believer that go with nothing but FRPP. The guy that installed the second set is a Ford Master tech with 17 years of experience. He has done over 1000 gear installs, so he knows what he is doing. Now you might get lucky and yours come out perfect, but if you want to avoid headaches and stress, send the gears back for some FRPP. I am stuck with mine until i go procharged and then i will just get them swapped out for some FRPP 3.73's.
drag0nfan's04GT
New Member
spederman said:
i got motive gears because I heard they were really good. thanks for sharing your experience, i hope my gears don't whine. i've heard of most motive gear installs went pretty well.
how did your car feel after having those gears installed?
