I just bought a car on thursday and when driving on the freeway my speedometer says im going about 90-95 and im going with the flow of traffic. I'm guessing its about 80mph. The speedo says im going 85 and 2500rpm. I believe that the previous owner had gears but i cant say because i bought it from a dealership (independent one not a big one) Is there anyway to tell what gears are in the car?
Just bought a car and speedo is way off.
- Thread starter mat82284
- Start date
ShortThrow50
Member
open up the rear diff. If they are ford racing gears., Most likely they are. The gear ratio will be stamped iin the ring gear
I just bought a car on thursday and when driving on the freeway my speedometer says im going about 90-95 and im going with the flow of traffic. I'm guessing its about 80mph. The speedo says im going 85 and 2500rpm. I believe that the previous owner had gears but i cant say because i bought it from a dealership (independent one not a big one) Is there anyway to tell what gears are in the car?
anything more simpler? like someone being able to compare rpms to speed. Or something else.
04YELLOWGT
Active Member
Yes some on here can tell you which ones you have. I think those would be 3.73 you have. You need to pick up a hand held tuner or a speedcal though.
stangman
15 Year Member
you can jack the rear of the car up & compare the rotations between the driveshaft & tires, to tell exactly what gear is in it. if the tires go around 3 & 3/4 times (3.73 to be exact) per one rotation of the driveshaft, you have 3.73 gears
Dusstbuster
I love meat more than anything! I just have a spec
You have major issues with double posting dude...
Anyways no, you'd want the wheels to spin 3.73 times per 1 rotation of the driveshaft. Imagine how fast your engine would have to be turning to get on the interstate.
Anyways no, you'd want the wheels to spin 3.73 times per 1 rotation of the driveshaft. Imagine how fast your engine would have to be turning to get on the interstate.
Ok thanks. Yeah for some reason my internet is really tripping and stangnet is going really slow it takes about 2 mins for my page to load when i click post. Maybe this is why its double posting? dono but thanks for the information ill have to jackup the car tomarrow and check it out. Thanks
trinity_gt
10 Year Member
You could've also used some simple math:
A 92MPH reading when going 80MPH is 12MPH high; 12/80=0.15 or a 15% high reading. You could then multiply 3.27 -- the stock ratio -- by 1.15 to get a close approximation to the gears in the rear: 3.76.
Select the nearest ratio available, 3.73.
A 92MPH reading when going 80MPH is 12MPH high; 12/80=0.15 or a 15% high reading. You could then multiply 3.27 -- the stock ratio -- by 1.15 to get a close approximation to the gears in the rear: 3.76.
Select the nearest ratio available, 3.73.
Dusstbuster
I love meat more than anything! I just have a spec
thanks but abott doesnt have it setup for that heres there wierd graph.
http://www.abbott-tach.com/calibration.htm
trinity_gt
10 Year Member
You asked a way to tell what gears are in there. The math gives a pretty close approximation.
For your corrector, if you use the 1.15 factor (i.e. you're reading 15% higher than you should), take the reciprocal -- 1/1.15 == 0.8696 -- and select the nearest switch settings:
0.870 0 0 1 0 0 0 0 0 0 1 1 1
stangman
15 Year Member
but the one absolute that he'd need there, is to know for a fact that he was going 80. & that would be a problem for anyone in that situation
He could use that diagnostic mode on the car and then drive to see what it's really turning. If his speedo says he's running 60 but the displays says he's running 55 then you know it's off by 5.
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