Gears ?
 

Is there a way I can tell if my car doesn't have the stock 3.27 gears on it? I have a 2000 GT that I got about 2 months ago. It seems like my speedo is off some, it reads a higher speed than what I think I'm actually going, and my RPMs don't seem right. At 65mph (which probably more like 60mph or less), I'm around 2k. I was thinking maybe the previous owner changed the gears and never recalibrated the speedo? Can someone explain this for me? Thanks.

I would say you should be about 2k around 65, that seems right to me.

Put your car up on jack stands. Get someone to help you if possible.
Place a piece of tape or a mark with a grease pencil on your drive shaft. With the parking brake off and the car in nuetral slowly turn the right rear tire, while turning count the amount of full revolutions the drive shaft makes for one complete tire revolution. This why you put the mark or tape on it, for a reference point. If your gears are stock 3.23's then it should make three full reveolutions and one quarter. If for instance it goes 3 and 3/4 turns then you have 3.73's. Four and a little would be 4.10's etc. By the way this assumes you have stock size tires.

cool, I'll do that. Thanks.

60 is 1850 on my 3.27's.

Yea it sounds like 3.73's to me man. Im at about 2000-2100 with my 3.73's at 60 mph.

lets us know what you fine out.... and if you have gears already installed one less thing you need to do except get it calibrated.

well nobody has asked this ovious question, are you Auto or Stick..because this could be a whole lotta somethign for a wholle lotta nothing..

-Mike :whip2:

it's an automatic

then there ya go..you have ths stock gears what you may be experirencing is the feeling of superiority that mustangs have over the common, car when all those 4 bangers are working hard to maintain or accelerate up to speed, the mustang's hearty v8 does it with a doubt ...no worries chum, you're car is ok. :icon_quee


-Mike :toothy9:

i have an 01 auto at 70mph your at 2100 rpms. your fine. get gears and you will be more happy

i'm at 2000rpm at 65 with my 3.73s. i have an 04 GT 5 speed.

tires size has no effect on that method of finding the gear ratio, you could have 33" mud tires and a 4.10 gear will still turn the d/s 4.1 times, as long as you t the tire 1 revolution.

tires size does matter if you are using the speedo to determine gear though.

I belive that it does make a difference. Tire diameter changes will affect your gearing. If I run a 28" tall slick as opposed to a 26" I will raise my final drive ratio. That is why many people with steep gears run a 26" tall tire n/a then switch to a 28" to run nitrous.

Oh ok sorry, didnt know that it was an auto. Now get them out and put in some 4.10s.

of course it will effect final drive ratio, because the distance around the outside of the tire i more if the diameter is more. BUT, we arent talking about final drive, we are talking about axle gear ratio.

If you are looking for gear ratio, by comparing tire to driveshaft, it doesn't matter at all, 1 axle rotation = number of D/S rotations = gear ratio.

It doesn't matter if you ave no tire on the axle at all, or a 3' diameter wheel, one 360* rotation of the tire = 1 axle rotation = D/s rotations = gear ratio.

I don't think we dissagree, I just think you just misunderstood what I said.

I see what you are saying. You are correct it can be done with the tire removed just like you said. Except I'm lazy and would not want to remove the tire. There are a couple of good online calculators to figure you gear also if you have aftermarket tires of a different size.

There is an ID tag on one of your rear cover bolts, look at it. If its there, chances are your gears are stock. If theres no tag, its been opened up.

Adam

you still miss my point, no matter what size the tire, 1 tire rotation = 1 axle rotation. we are looking for axle ratio.

tru dat