Need help recalibrating speedometer

fgtmustang95 · Apr 6, 2006

I recently had some 3.73 gears installed. What exactly do I have to do and where can I get what I need to correct the speedometer? Apparently I was going 130 mph down the access road but that just ain't right. Thanks for the input

urban96 · Apr 6, 2006

50resto.com sells a speedo gear. its under $10 and you just need to swap it out with the stock one (15min job)

or you can buy the dallasmustang speed cal that you wire into the VSS and it will recal. it for you. but its around $100

Danman765432 · Apr 7, 2006

Yeah I just got my trans rebuilt and im about 10 mph off right now since I have an 18 tooth speedo gear in, I really need a 16 tooth one but yeah they are cheap and very easy to install

fgtmustang95 · Apr 7, 2006

I have looked into the 50resto catalog but found they only have one 3.73 speedo gear but its listed for 96-98 Cobra. Under 94-98 they have no 3.73 speedo gear. Would the cobra 3.73 speedo gear work on my car? My 95 GT is a 5 speed by the way.

Danman765432 · Apr 7, 2006

I'm not really sure but as long as it has the same amount of teeth it should because I know that is what determines what your speedometer says. By mistake the place where I got my trans rebuilt and upgraded they put in a 3:73 speedo gear and it said i was going 40mph but i really was doing about 60mph. Also I believe there are some speedo gears up on ebay for like 10 buck that are 3:73s

fgtmustang95 · Apr 7, 2006

I may just end up trying out the Cobra speedo gear and see how that works. Its only like 8 bucks anyway. And just to make sure its recalibrated correctly, I'll ask a cop nicely to clock me as I speed by.

Danman765432 · Apr 7, 2006

I think the one you need is either 21 or 23 teeth but tomorrow I can find out definately for you. But don't take my word as of now since I am not completely sure

Danman765432 · Apr 7, 2006

I just went onto steeda's website and they have them, this is the info I got.

# Manual Transmissions with 8 Tooth Drive Gear
# 1990-1995 T-5 OEM
# 1996-1998 T-45 OEM Except Cobra
2.73 Gear Ratio / Yellow 18 Speedo Gear $9.95
3.08 Gear Ratio / Black 20 Speedo Gear $9.95
3.27 Gear Ratio / Red 21 Speedo Gear $9.95
3.55 Gear Ratio / White 23 Speedo Gear $15.95
3.73 Gear Ratio / White 23 Speedo Gear $15.95
4.10 Gear Ratio / White 23 Speedo Gear $15.95

http://www.steeda.com/

GRGT1994 · Apr 7, 2006

Danman765432 said:
I just went onto steeda's website and they have them, this is the info I got.

# Manual Transmissions with 8 Tooth Drive Gear
# 1990-1995 T-5 OEM
# 1996-1998 T-45 OEM Except Cobra
2.73 Gear Ratio / Yellow 18 Speedo Gear $9.95
3.08 Gear Ratio / Black 20 Speedo Gear $9.95
3.27 Gear Ratio / Red 21 Speedo Gear $9.95
3.55 Gear Ratio / White 23 Speedo Gear $15.95
3.73 Gear Ratio / White 23 Speedo Gear $15.95
4.10 Gear Ratio / White 23 Speedo Gear $15.95

http://www.steeda.com/

Notice how the 3.55, 3.73 and 4.10 use the same speedo gear. That is because the speedo gear cannot be physically large enough to properly correct for 3.73 or 4.10. In your case, your speedo will read 5% faster than you are actually travelling (and your odo will be artificially inflated by the same 5% factor).

I believe there is a secondary gear you can change that, with the proper speedo gear, can get you even closer than 5%. But I think that gear is inside the transmission, and I have never heard anyone talk about how hard or easy that one is to replace.

If you want to get your speedo dead on, you prolly need to get the speed cal. That's what I did, and it works great for me.

Oh and as far as asking a nice cop to radar you, there is another way to test the accuracy. Just go to the flatest, straightest run of highway in your area. Reset your trip odometer right at a mile marker. Then drive 10 miles. At the 10th mile marker, note how far your trip odo reads. Every 10th a mile high or low from reading exactly 10 miles would equate to a 1% error in your odo and speedo. You can do the same test at only 1 mile, but you get a more accurate reading at 10 miles (travel farther for more accuracy).

Danman765432 · Apr 7, 2006

or you could just get a friend to pace you or if you have a speed trap in your town just go through that

gustang818 · Apr 7, 2006

The other problem with the white gear is that it gets chewed up and leaves little pieces of plastic teeth in your tranny. I heard the white gear is really for a chrysler. I have the red gear now and do the math to figure my speed.

final5-0 · Apr 7, 2006

Somthing that needs to be considered is, peeps who tell you about their experiences with this ratio and that number of teeth on the driven gear are great and all

but

that don't mean you will obtain the exact same results.

Tire size makes a diff and the more diff between yours and theirs will cause the greater diff in your results

Some t5's had different drive gears which I've seen from time to time that can make a diff as well.

besides all of that .............

Who says everybodys speedos have the same degree of accuracy

I'd say if you have the same size drive gear as most t5's and you use a 23 tooth driven gear, that is the closest you are gonna get without ......

speed cal
or
drive gear change

I run 25" tall tires and my speedo reads about
+2 mph around town
+4 mph at highway speeds
most likely +6 around 100 mph

A speedo error that small concerns me not in the least bit

to make me spend 100 bux on some magic box

or

tear the trans apart to replace the drive gear which would then cause me to have to buy another driven gear

play with this and you'll see what I'm trying to say here

http://www.allfordmustangs.com/Detailed/608.shtml

btw ... Some have had issues with the 23 tooth driven gear wearing quickly as its not an exact, perfect fit for our cars. I've been runing one since 97 but my 95 is a weekend toy only.

Grady

Black95GTS · Apr 7, 2006

final5-0 said:
Somthing that needs to be considered is, peeps who tell you about their experiences with this ratio and that number of teeth on the driven gear are great and all

but

that don't mean you will obtain the exact same results.

Tire size makes a diff and the more diff between yours and theirs will cause the greater diff in your results

Some t5's had different drive gears which I've seen from time to time that can make a diff as well.

besides all of that .............

Who says everybodys speedos have the same degree of accuracy

I'd say if you have the same size drive gear as most t5's and you use a 23 tooth driven gear, that is the closest you are gonna get without ......

speed cal
or
drive gear change

I run 25" tall tires and my speedo reads about
+2 mph around town
+4 mph at highway speeds
most likely +6 around 100 mph

A speedo error that small concerns me not in the least bit

to make me spend 100 bux on some magic box

or

tear the trans apart to replace the drive gear which would then cause me to have to buy another driven gear

play with this and you'll see what I'm trying to say here

http://www.allfordmustangs.com/Detailed/608.shtml

btw ... Some have had issues with the 23 tooth driven gear wearing quickly as its not an exact, perfect fit for our cars. I've been runing one since 97 but my 95 is a weekend toy only.

Grady

You're right. But also consider its not only your speedo that is reading too fast, your odometer is reading too high. (for the poster) If you ever think of selling the car, telling the guy buying it that there sould be 10K less miles cause of gearing is gonna be a tough statement to back up...

Plus I'm crazy about accurate speedos; I bought the speedcal.

Adam

final5-0 · Apr 7, 2006

Black95GTS said:
You're right. But also consider its not only your speedo that is reading too fast, your odometer is reading too high.

Adam

I have thought about that from time to time

I just don't put enough miles on my car for it to matter

but

for a dd, it could make a diff for sure

Grady

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