Luna

iTrader: (6)

Hey guys, not really sure where this belongs so I threw it in here....

I have a feeling my speedometer is off a little bit... roughly 10mph at about 80mph or so , gets worse as speed increases....

I am thinking maybe my car has had different gears installed and the speedo was never recalibrated, how much of a MPH difference might I see with a slightly larger gear, the door code says 273 and I doubt whatever is in there is much larger than like a 323 or 342.

If it is different how would I go about finding out exactly what size gear is in there??

Also when I took the car to the track the speedo read near 120mph trap speed where my ET slips were no higher than 104mph

camaroextra

iTrader: (10)

it could be, do you have stock rims and tires?

you need to get exact mph error numbers then you could do some simple math to figure it out. get someone else to drive next to you at a set speed and find the difference

Luna

iTrader: (6)

yea stock wheels and tires, I never thought about it before because I got pretty good gas mileage.

I'm gunna get my buddy to drive next to me to figure out how far its off if at all next week .

Once we do that is there a definite mathematical way to figure out the exact gearing that is in there?

camaroextra

iTrader: (10)

yeap. just note the rpm on both cars, the easiest way to calculate it is off of the rpm's at a given speed, but you need the other car to get the actual speed

Luna

iTrader: (6)

Wouldnt the other car have to have the exact same gearing??

Ell Ess Won

Not to hijack the thread, but what gears do I have?

40mph = 2k rpms
60mph = 3k rpms.

Luna

iTrader: (6)

Well your sig says 373 and I would say thats about right since 2000RPMs is about 70mph on my car with the supposed 273 gears

Luna

iTrader: (6)

What speed should 2000 RPMs put me at with 273 gears what about with 323 ?

2001NBMZ28

I always use www.f-body.org/gears/ to check my speedo for my 2.73 to 3.42 swap after tuning.

Speed Density

iTrader: (38)

my speedo is at 55 when im really going 35. IT gets worse up higher, at like 90-100 my speedo is at 130-140. Thats with 4.10s in an A4.

meatman

iTrader: (20)

I just went from 273s to 373s. I was pacing cars on highway prob doing 70-75 and I was running 100 mph at about 2500 rpm.......have an auto by the way.

FUN LS1

Being able to modify the gear and rim/tire parameters was one of the main reasons I got my Predator tuner. You could just find a shop to change it for you for $50...

Xtnct00WS6

iTrader: (8)

So let me make sure I understand this.

Taller gear than stock (373 or 410) + no tune = Faster Speed than what your going

and

Higher gear tune + stock gears = Slower Speed than what your going

Is that right?

mondi2002

iTrader: (11)

Yes, My spedo shows around 5-6 mph slower than
my actual speed because I went from 4.10 back to 3.42
when I blew my rear. (Spedo is calibrated for 4.10's)

baddogz28

iTrader: (6)

I was more worried about my odometer than the speedo when I got my 9" installed, bigger gears + untuned will pile those miles on FAST.

JerseyLS1TA

iTrader: (2)

Damn some of your speedos are off I would be getting tickets left and right if mine was that off. I have 2.73 gears in my 99 auto T/A and cruising on the highway at 2,000 RPM's I am doing 80mph