do i have stock gears?

ocbaud · Oct 8, 2005

ok, driving around in the gt today i noticed people seemed to be speeding, A LOT. it seems like my speedo could be off, or it could just be me getting used to the new car.

in 5th gear @ 70mph its showing 2,000 rpm's

if that is correct, then i dont know

jasonh_86 · Oct 8, 2005

i dunno... that's about the same mph/rpm i usually run, but maybe i'm wrong..

Red2000GT · Oct 8, 2005

Sounds like stock to me.

sgarlic · Oct 8, 2005

Change your tires to the wrong size or change rim size lately or something? That'll throw speedo off. 2krpm is about what I have as wel at 70mph.

ponysarepretty · Oct 8, 2005

sgarlic said:
Change your tires to the wrong size or change rim size lately or something? That'll throw speedo off. 2krpm is about what I have as wel at 70mph.

I think you are all missing the point, the very fact that he seems to be going slower than he should would be an indication that someone changed the gears and did not recalibrate the speedometer.

A good way to test is to have a friend drive by with the cruise control on at a certain speed then you drive fast enough so as to catch him shut it down and compare how fast you wre going. If you are going the same speed, no problem, you have stock gears and a correct speedo. If you are going faster, it would indicate a numerically lower gear which has not been recalibrated. And if you are going slower, you probably have aftermarket higher gears which have not been recalibrated.

Or you can go through a speed trade (they have them near my school) and see if your speedo matches the speed of the display

sgarlic · Oct 8, 2005

ponysarepretty said:
I think you are all missing the point, the very fact that he seems to be going slower than he should would be an indication that someone changed the gears and did not recalibrate the speedometer.

No, it doesn't indicate a gear change, since 2 or 3 people above with stock gears run at the same RPM as him. He has stock gears, so I offered another possibility. Changing tire size/rim size effects speedometer. A bigger rim and tire combo will make it read slower than you're actually going, smaller rim/tire the opposite.

ocbaud · Oct 8, 2005

sgarlic said:
No, it doesn't indicate a gear change, since 2 or 3 people above with stock gears run at the same RPM as him. He has stock gears, so I offered another possibility. Changing tire size/rim size effects speedometer. A bigger rim and tire combo will make it read slower than you're actually going, smaller rim/tire the opposite.

so i guess people were just speeding then......

i'm running 245/45/17's all around so the tire size is right.

CrazyHorn · Oct 8, 2005

What would be the speed of the car with 4.10 or 3.73 at 2000rpm ?

manny · Oct 8, 2005

i have 373's and an automatic and at 2000 rpm's i'm running around 66 mph.

MaxedGT · Oct 8, 2005

If the speedo isn't calibrated, the rpm and speed will still match stock, but he'll not be really travelling the indicated speed!

ocbaud · Oct 9, 2005

86mph = 2600 rpms in 5th gear

is that correct?

40 mph = 2000 rpms in 4th gear

but i drove my old 02' v6 tonight and it showed the following:

45 mph = 2000 rpms in 4th gear

flashstang04 · Oct 9, 2005

Sounds like 3.23 to me also

bdcardinal · Oct 9, 2005

the other way to find out is to take off the diff cover and count the teeth on the ring and pinion gears.

ocbaud · Oct 10, 2005

ok, i'm confused.....

http://www.stangsource.com/calculators.cgi?calculator=1

i'm using that calculator and its coming up funny. we have a 3.27 stock gearing right?

at 2400 rpm i should be at 83mph

and at 2600 rpm i should be at about 90

the first picture i posted seems to be about right.

the second picture seems off by about 4mph

also, in 4th gear at 2000 rpms, i should be reading at 46mph where i was actually reading 40 mph

my old v6 was showing 2000 = 45mph tonight too......

could it be a problem with the after market gauges that were installed and how the needle was positioned?

MaxedGT · Oct 10, 2005

Jack up both wheels. mark the driveshaft. spin your rear wheels one turn, while counting how many times your driveshaft rotates. EG. if your driveshaft spins about 3 1/4 turns you've got 3.27. If it spins 3 3/4, 3.73, if it spins over 4 turns, 4.10 etc.
Both wheels have to spin together. That shouldn't be a problem if your limited slip is ok.
You can't use rpm and speedo readings if your speed hasn't been calibrated!
Also if your needles arn't positioned right after the gauge install, both tach and speedo could be wrong.

grinder · Oct 10, 2005

no prob to find out

There is a metal tag on the right side of your diff cover...held on by one of the cover bolts... The gear is noted on this tag.. bottom left number will show the ratio like this.. 3L27 XXX XXXX....This would be a 3:27 gear.. 3:73 would be 3L73 and so on. The other numbers on the tag are the date of manufacture, etc.

bdcardinal · Oct 10, 2005

grinder said:
There is a metal tag on the right side of your diff cover...held on by one of the cover bolts... The gear is noted on this tag.. bottom left number will show the ratio like this.. 3L27 XXX XXXX....This would be a 3:27 gear.. 3:73 would be 3L73 and so on. The other numbers on the tag are the date of manufacture, etc.

thats all well and good, however someone who did a gear swap could very easily left that tag on there. also GTs didnt come with 3.73s fron the factory

goshia · Oct 10, 2005

That is what I get on my 04 GT. 70MPH @2K and 75MPH @2.2K
with Stock gears.

do i have stock gears?

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