Speedo is wayyy off: what gears do I have?

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 21, 2004

#1

• Nov 21, 2004

• #1

Hi!

The speedo on my Stang GT 2001 (T3650) is wayyy off. At ~2000 RPM at 75 mph (speedo), I'm in reality going at 55-57 mph according to the cars following me.

There were some threads with links to calculate everything, but I didn't find them. What gears do I have?

Thanks

 

98stangv8

Active Member

Oct 3, 2003

1,036

0

36

49

fayetteville, nc

6to8mustang.com

Nov 21, 2004

#2

• Nov 21, 2004

• #2

i would "guess" 3.73's...but that is just a guess...

how do you not know what gears you are running? did you just buy the car that way?

 

UVBNHAD

New Member

Aug 18, 2004

144

0

0

McCalla, AL

Nov 21, 2004

#3

• Nov 21, 2004

• #3

If it's not gears have you swapped out the guages lately? If you don't do the needles right they will be way off.

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 21, 2004

#4

• Nov 21, 2004

• #4

98stangv8 said:

i would "guess" 3.73's...but that is just a guess...

how do you not know what gears you are running? did you just buy the car that way?

Click to expand...

Yep, I bought the car that way.

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 21, 2004

#5

• Nov 21, 2004

• #5

UVBNHAD said:

If it's not gears have you swapped out the guages lately? If you don't do the needles right they will be way off.

Click to expand...

Nope! Everything's all original.

 

Cobra Jay

Member

Apr 7, 2004

889

0

16

53

Motor City

Nov 21, 2004

#6

• Nov 21, 2004

• #6

Xcessiv said:

Hi!

The speedo on my Stang GT 2001 (T3650) is wayyy off. At ~2000 RPM at 75 mph (speedo), I'm in reality going at 55-57 mph according to the cars following me.

There were some threads with links to calculate everything, but I didn't find them. What gears do I have?

Thanks

Click to expand...

If you're still running 245/45/17's that gives you a tire height of 25.6811.
Assuming you're in O.D.(5th gear)

Tire Height=25.6

O.D. ratio =.62

RPM=1925(2000 on tach)

MPH=55

R&P ratio= 4.30


or

Tier Height=25.6

O.D. ratio=.62

RPM=1902(2000 on tach)

MPH=57

R&P ratio=4.10


www.randysringandpinion.com
It's hard to tell because you havn't been to specific and your cars tachometer won't give you a 100% exact reading.

Jack the rear of the car up off the ground and put some jack stands under it to support the car.

Make a mark on a tire and 1 on the driveshaft.

Have someone rotate the tire one complete revolution while you count how many times the drive shaft rotates. A little over 4 would=4.10 a little over 4 1/4 turns on the D/S= 4.30

hope this helps.

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 21, 2004

#7

• Nov 21, 2004

• #7

Wow! This is exactly the kind of answer that I was looking for.

Thanks alot!

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 21, 2004

#8

• Nov 21, 2004

• #8

I'm just anxious to see how this will translate the main driveability of the car in daily driving. I really don't think that 4.30s make your car faster.

I think that I'll look for some Nittos DR...

 

Cobra Jay

Member

Apr 7, 2004

889

0

16

53

Motor City

Nov 21, 2004

#9

• Nov 21, 2004

• #9

Xcessiv said:

I really don't think that 4.30s make your car faster.

I think that I'll look for some Nittos DR...

Click to expand...

Go drive a stock Stang with 3.27's and then one with 3.73's,4.10's or 4.30's and then tell me that the gears do nothing for them!

Stay away from the Nitto DrR's. Get some BFG or M/T Dr's!

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 22, 2004

#10

• Nov 22, 2004

• #10

GT JAY said:

Go drive a stock Stang with 3.27's and then one with 3.73's,4.10's or 4.30's and then tell me that the gears do nothing for them!

Stay away from the Nitto DrR's. Get some BFG or M/T Dr's!

Click to expand...

Ok... I gotta admit that it really wakes up the car. I was just wondering if I could get any traction on the street when wanting to play a bit.

 

X

Xcessiv

Member

Jul 16, 2004

187

0

16

Nov 28, 2004

#11

• Nov 28, 2004

• #11

I did the driveshaft test today and I officially have some 4.10s under there. I'm pretty happy, I was planning to install theses anyway.

Now, I just gotta learn how to drive this beast on standing starts.