| Speedometer
Information
[SF] Question: "Is a different
speedo cable required with Autometer gauges? The fitting on mine is
threaded and the little white clip on the cable won't hold it on.
An adaptor maybe?"
Answers: [PL] "I have the
Autometer speedometer and used the factory cable, VDO makes an
adapter that goes right on to the factory cable and has a square pin
in it that slides into the speedometer. Then you just screw it
together and the whole setup cost like $10"
[JH] "My Autometer speedo gage
is mounted to the right of the steering wheel. The cable comes in
from the firewall, instead of the footbox. The stock cable was too
long, so I
made a loop and took up the slack. The loop is in the tunnel area
and is secured by zip-ties. Works fine. I tried shorter cables from
a Taurus and a Escort, but they were about 1" too short."
[MR] "My stock cable was
68" long. Going through the FFR supplied hole in the top of the
footbox works but is a little kinky and the stock cable length seem
a bit short for nice smooth routing. I had a custom stainless
jacketed cable made by ACI (616) 327 1991 in Michigan in an 80"
length. I routed the cable through a notch in the top edge of the
front of the footbox aluminum and a mating notch in the inside top
footbox cover. Cost was in the 75 dollar range. I have no idea
how the person above got a stock cable so long he could put a dipsy
doodle in it!"
Speedo Gear Chart
[KevinK] Source: The Corral Web
An important
consideration during the gear swap is finding the right drive/driven
speedometer gears per your application. Ford used a seven (7) tooth
drive gear in the 1983 to 1989 T-5's, then switched to an eight (8)
tooth drive in 1990 (used through 1995). If you have 3.73's with an
eight-tooth drive, and the highest driven gear with twenty-three
(23) teeth, the speedometer still reads 5% fast. With the limited
number of gears available, the combinations are (number in the table
is the driven gear tooth number to be used with left hand gear ratio
and drive gear column):
|
Rear end ratio / Speedo drive
|
Six (6) tooth drive
|
Seven (7) tooth drive
|
Eight (8) tooth drive
|
|
3.27
|
16
|
19
|
21
|
|
3.55
|
17
|
20
|
23
|
|
3.73
|
18
|
21
|
n/a
|
|
4.10
|
20
|
23
|
n/a
|
|
4.30
|
21
|
n/a
|
n/a
|
|
Part number
|
E3ZZ-17285-B
|
E3ZZ-17285-A
|
F0ZZ-17285-A
|
|
Color
|
Black
|
Yellow
|
Green
|
Note: The above combinations are
based on tires with or very near to stock diameter (225/55-16 is
25.74").
This
is topic Speedo Cable Gear Chart? in forum Cobra
Grandstand at FFCobra Discussion Forums.
To visit this topic, use this URL:
http://www.ffcobra.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=002157
Posted by teamfour (Member # 615) on April 27, 2002,
09:19 PM:
In the old days of the "other" forum, there was a
chart produced that listed the speedo gear required given your
tire size and rear end gears. Anyone have it? I am running a
standard T-5, 255-60-15s, and a 3.55 rear. I had put a 23T
gear in, but it is nowhere close to accurate.
Posted by d isham (Member # 45) on April 27, 2002,
09:33 PM:
Here you go.
http://chris.kellnet.com/chambers/speedo_gears.htm
http://www.hanlonmotorsports.com/t5speedo.asp
Doug
Posted by teamfour (Member # 615) on April 27, 2002,
09:50 PM:
Thanks Doug! I looked at the tranny gear before putting the
tranny in the car and the gear was white, which according to
most charts is a 7 tooth gear. This led me to believe that I
needed a 23T. However, I read that 1990 trannys came with a 8T
gear which would require a 21T speedo gear. What the heck, I
will just buy the 21, put it in and see what happens
Posted by BillG (Member # 499) on April 27, 2002, 11:18
PM:
Well Doug, I used booth sites and the first says I need a 23
tooth gear, and the second says I need a 19 tooth gear? What
one is right? Right now I am running 3.55 rear gears 93 tranny
and 275/50 15" tires that are suposed to be 25.83"
tall. I have a 20 tooth gear in now and in a measured mile I
am about 1/10 of a mile to fast. Will the 19 tooth slow it
down or do I go with the 23 tooth ? Very confused at this
point.
Posted by PiMan (Member # 22) on April 28, 2002, 08:46
AM:
Is there a similar chart for the Tremec TKO?
Or, does anybody know what cable I should buy for a TKO and
the Stewart-Warner speedo? I am running a 3.55 rear end with
tires 26.0 inches in dia.
Or, deos anyone know who would know?
Thanks for you help, as always.
Posted by d isham (Member # 45) on April 28, 2002,
09:55 PM:
Well, I can tell you that I am running a T-5Z w/ 19 tooth,
275-50-15 and 3.55 rear and I'm off (if I remember correctly)
on the speedo by about 10 mph too fast. Last I checked it was
7 mths ago and just left it alone. Guess I will go back and
check it again. May be this time I'll actually change out the
gear for the correct one. I'm going to try a 21T this time.
Doug
Posted by MikeBraddock (Member # 627) on April 29,
2002, 11:00 AM:
After reading your posts on this thread it sounded like a very
interesting question/problem, so here's what I was able to
find:
First, another driven gear (ie the gear on the end of the
speedo cable) chart:
http://www.ddperformance.com/speedo_gear_chart.htm
Next, the driven gear you need depends on what year T5 you are
running. Ford made changes in '90, so you'll need a different
gear for an '83-'89 vs a '90 to '95 T5 trans. From what I've
read (which wasn't in the FRPP catalog, so it may not be 100%)
Ford switched the drive gear (ie the gear on the output shaft
of the trans which spins the speedo gear) in the T5 in 1990. The
‘83-’89 T5’s have a 7 tooth drive gear and the ’90 –
’95 T-5’s have an 8 tooth drive gear.
Here's an example off how these ratio’s are calculated:
driven gear teeth = (drive gear teeth * axle ratio *
(63360/(3.14*D))/1000
The "63360" is the number of inches in a mile;
3.14*D (the tire diameter) is the rolling circumference in
inches.
Using an early model T5 with 3.73 gears and a standard 26”
tall tire, the above formula gives: (7 X 3.73 X 776)/1000 =
20.2 (which is close enough to the 20T speedo gear). This
would be the correct calculation for a pre ’90 T5 since it
uses the 7 tooth drive gear.
As a side note, the 23 tooth driven gear is not a Ford gear,
so it doesn’t last too long and should probably be avoided.
Instead, it’s suggested that you change the drive gear in
the tailshaft and use a different (OEM Ford) gear.
Instructions on changing out the drive gear can be found at
the bottom of the following page:
http://chris.kellnet.com/chambers/speedo_gears.htm
One of the more common questions
on the Mustang tech boards is "What speedometer gear do I need to go with
my new 3.73:1 gears?". Here's a simple calculator I drummed up to solve
the problem. Enter the data from your drive line setup and hit 'Go Figure'.
Here's the part numbers for
the various driven gears (courtesy of the 2000 Ford Racing Performance
Parts catalog):
| Manual
T5 |
Automatic |
|
Teeth
|
Part Number
|
Color
|
Teeth
|
Part Number
|
Color
|
|
16
|
C0DZ-17271-A
|
Wine
|
16
|
D0AZ-17271-A
|
Blue
|
|
17
|
C3DZ-17271-C
|
White
|
17
|
C7SZ-17271-A
|
Green
|
|
18
|
C0DD-17271-B
|
Yellow
|
18
|
C7SZ-17271-B
|
Gray
|
|
19
|
C0DZ-17271-B
|
Pink
|
19
|
C7VY-17271-A
|
Tan
|
|
20
|
C1DZ-17271-A
|
Black
|
20
|
C8SZ-17271-B
|
Orange
|
|
21
|
C4OZ-17271-A
|
Red
|
21
|
D0OZ-17271-B
|
Purple
|
|
23*
|
DFM-17271-A
|
White
|
* Available from Mustangs
Unlimited @ 1-800-243-7278
I've yet to see a 22 tooth driven
gear available for the T5, but I've been told that Mopar dealers may have
them. Refer to our Gear Swap
page for details on installing the driven gear in a T5. The 23 tooth
driven gears are notorious at being short lived. Mine lasted only months
before stripping all the teeth of itself. I think the root diameter is
so small (in order to fit so many teeth on it), that it creates a bad mesh
with the drive gear.
Unfortunately, the drive gear
on the automatic transmissions (AOD) is integrally machined into the output
shaft. This means that you'd have to replace the entire output shaft to
change your drive gear to obtain the correct drive/driven gear ratios.
This is pretty expensive and impractical. In this situation, you're better
off obtaining a speedometer correction box to correct the speedometer readings.
Email me if you need a source for the correction box.
|
Manual Transmission
Drive Gears
|
|
Teeth
|
Part Number
|
Color
|
|
6
|
E3ZZ-17285-B
|
Black
|
|
7
|
E3ZZ-17285-A
|
Yellow
|
|
8
|
F0ZZ-17285-A
|
Green
|
The
drive gear in a T5/T45 transmission is pretty easily changed. Follow the
steps below:
-
Drain and remove the transmission.
-
With the transmission in neutral,
remove the shifter cover housing (four bolts) and shifter assembly.
-
Using a small punch, drive the
roll pin down far enough to disengage the slider rail. Do not drive it
all the way out of the shift gate.
-
Remove the bolts attaching the
tail shaft housing to the main transmission case.
-
Slide the tail shaft housing, complete
with shift gate, off the transmission. Be sure not to loose the detent
ball and spring when the shift gate comes clear of the slider rail. Go
ahead and remove the roll pin completely at this stage so that it can be
driven in from the top side at reassembly.
-
Depress the spring clip that retains
the drive gear and slide the drive gear off the output shaft.
-
Install the new drive gear and
reassemble the tail shaft housing in the reverse order. A little petroleum
grease will help hold the detent spring and ball in place while reassembling
the tail shaft housing.
|
If you measure your tire diameter and don’t end up close
enough to a stock OEM driven gear, you have two choices (that
I found). First, you swap the drive gear as well as the driven
gear (if that calculation comes out closer to a whole number
of teeth matching a driven gear Ford sells). As an example,
let’s say you have a ’91 T5 (8 tooth drive gear) with 3.73
gears and a 26” tall tire. The above formula would result in
a 24.3 tooth gear, which isn’t available. Instead, you can
change the drive gear to a 7 T and run a 21 T driven gear, as
in the previous calculation.
Your second option if you desire an accurate speedo, can’t
buy a driven gear that has the correct number of teeth, and
you don’t want to change the speedo drive gear in your
tranny, is to buy an inline correction box that a few speedo
shops sell. With this box, you tell them your rear gear ratio,
your rear tire size, the number of drive teeth, the number of
driven teeth and they will build for you a calibration box
that splices into your existing speedo cable. Cost is between
$75 and $100.
The above formula is the one used in the gear calculator found
on the chris.kellnet.com webpage noted previously. For me at
least it sometimes helps to know where the numbers in these
calculations come from. His program also calcs. the error in
your speedometer reading based on the recommended drive gear,
so you can decide whether you will be satisfied with it or
not. For example, the error on the first calculation for the
early model T5 with 3.73’s and a 26” tall tire would be:
error = [(20.2/7) – (20/7)] / (20.2/7) = [20.2 – 20] /
20.2 = 0.99%
Which means the speedo would then indicated velocities that
are about 1% higher than actual.
I hope this helps.
Mike
Posted by MikeBraddock (Member # 627) on April 29,
2002, 11:29 AM:
Doug,
Here’s what I get for your setup:
D = 25.8”
Your T5Z should have an 8T speedometer drive gear. Based on
that, I calculate your desired driven gear would be a 22
(22.17). Ford only makes a 22T driven gear for automatics, and
I don’t think they are interchangeable (different part
numbers).
Using your current 19T driven gear, I calculate an error of
about 14% (high). You said you were off 10 mph, but at what
speed? If it was around 70 mph, then this calculation is
agreeing with what you measured.
In your case, I would recommend the following:
If you swap to a 21T, you will have an estimated error of 5.3%
(high), which is a definite improvement over what you have
now, for very little investment and labor.
To get closer than that, you will need to swap the tranny
drive gear to a 7T and go with a 19T driven gear on the
speedometer cable, which would result in a calculated error of
approx. 2.1% (high).
Finally, if you prefer to be this accurate, but want the error
to be on the low side, you can swap the tranny drive gear to a
6T and go with a 17T driven gear on the speedometer cable,
which would result in a calculated error of approx. 2.2%
(low).
By the way, I forgot to mention in my last post that there are
three manual tranny speedometer drive gears available from
Ford: 6, 7 and 8T. Their part numbers and colors are
Posted by MikeBraddock (Member # 627) on April 29,
2002, 11:38 AM:
Lee,
Here’s what I get for your setup:
D = 27.0”
If your T5 is an ’89 or older, it should have a 7T
speedometer drive gear. Based on that, I calculate your
desired driven gear would be a 19T (18.5). Using your current
23T driven gear, I calculate an error of about 24% (low). With
a 19T driven speedometer gear, your error would be closer to
2.5% (low).
If your T5 is a ’90 or newer, it should have an 8T
speedometer drive gear. Based on that, I calculate your
desired driven gear would be a 21T (21.2). Using your current
23T driven gear, I calculate an error of about 8.6% (low).
With a 21T driven speedometer gear, your error would be closer
to 1% (high).
I hope some of this information will be helpful
Mike
Posted by MikeBraddock (Member # 627) on April 29,
2002, 11:48 AM:
Bill,
Just so you didn't think I forgot about you , here’s what I
get for your setup:
D = 25.83”
Your T5 should have an 8T speedometer drive gear. Based on
that, I calculate your desired driven gear would be a 22
(22.17). Using your current 20T driven gear, I calculate an
error of about 9% (high). As I told Doug, I don’t think
Ford’s 22T speedo gear will fit the T5 as they have
different part numbers (I could certainly be wrong on this!).
In your case, I would recommend the following (which is very
similar to what Doug needs):
If you swap to a 21T, you will have an estimated error of 5.2%
(high), which is again, a definite improvement over what you
have now, for very little time and money.
To get closer than that, you will need to swap the tranny
drive gear to a 7T and go with a 19T driven gear on the
speedometer cable, which would result in a calculated error of
approx. 2.1% (high).
Finally, if you prefer to be this accurate, but want the error
to be on the low side, you can swap the tranny drive gear to a
6T and go with a 17T driven gear on the speedometer cable,
which would result in a calculated error of approx. 2.2%
(low).
Mike
Posted by d isham (Member # 45) on April 29, 2002,
11:50 AM:
Mike,
What great responses. Thanks for the detailed info on my
specific application.
quote:
Using
your current 19T driven gear, I calculate an error of about
14% (high). You said you were off 10 mph, but at what speed?
If it was around 70 mph, then this calculation is agreeing
with what you measured.
My speed
was 70 mph so your calculations are in deed correct. 14% error
is huge. I think I'll swap out to a 21T. With a 21T hopefully
the 5.3% error will save me from a few potential speeding
tickets.
Out of couriousity, what is involved in swapping out a driven
gear (to a 7T) w/ an already installed tranny? May be more
work than I want to tackle at this point.
Thanks again,
Doug
Posted by MikeBraddock (Member # 627) on April 29,
2002, 11:54 AM:
PiMan,
I believe a tremec 3550 and TKO use the same drive and driven
gears as the T5. You (or I ![[Big Grin]](../ubb/biggrin.gif)
) should contact someone who would know for sure, like Mike
Forte. Assuming they are the same, I would venture to guess
the tremec uses an 8T drive gear, so in your case, you would
want a 22T gear, which I don't think you can get, so either go
with a 21T, which will give you a 4.5% error on the high side,
or do what I suggested to Doug and Bill and swap the drive
gear to a 6T and run a 17T speedo driven gear to end up with
around 2.8% error on the low side...
I will ask Mike next time I speak with him if the tremec
speedo gears work the same as the Ford gears. If you find out,
please let us know !
Thanks.
Mike
Posted by MikeBraddock (Member # 627) on April 29,
2002, 12:25 PM:
Doug,
The tranny has to come out to replace the speedo drive gear.
Here’s a reprint from the chris.kellnet page describing
what’s involved to swap out the speedo drive gear:
The drive gear in a T5/T45 transmission is pretty easily
changed. Follow the steps below:
1. Drain and remove the transmission.
2. With the transmission in neutral, remove the shifter cover
housing (four bolts) and shifter assembly.
3. Using a small punch, drive the roll pin down far enough to
disengage the slider rail. Do not drive it all the way out of
the shift gate.
4. Remove the bolts attaching the tail shaft housing to the
main transmission case.
5. Slide the tail shaft housing, complete with shift gate, off
the transmission. Be sure not to loose the detent ball and
spring when the shift gate comes clear of the slider rail. Go
ahead and remove the roll pin completely at this stage so that
it can be driven in from the top side at reassembly.
6. Depress the spring clip that retains the drive gear and
slide the drive gear off the output shaft.
7. Install the new drive gear and reassemble the tail shaft
housing in the reverse order. A little petroleum grease will
help hold the detent spring and ball in place while
reassembling the tail shaft housing.
Mike
Posted by BillG (Member # 499) on April 29, 2002, 03:27
PM:
Thanks Mike, I think I will go with the easy fix, 21 tooth
gear. 5% should equal 105 mph at 100 mph. should be close
enough to keep me out of trouble.
Thanks again, Bill
Posted by MikeBraddock (Member # 627) on April 29,
2002, 08:56 PM:
No problem Bill. Glad I could help. I think that's what I
would do too.
Mike
Posted by PiMan (Member # 22) on April 30, 2002, 10:28
AM:
Mike, thanks for the help.
Mike Forte confirmed that the TKO runs a 7 tooth gear, so I
ordered up the 20 tooth cable set from him.
Posted by MikeBraddock (Member # 627) on April 30,
2002, 08:40 PM:
PiMan,
You beat me to it . Mike emailed me back today and told
me the tremec 3550 and TKO both use a 7T speedo drive gear.
Thanks for posting!
In your case with the 7T gear, 3.55 gears and 26" tire,
wouldn't you want a 19T gear? I calculate 19.27T, so a 19T
drive gear would give you an error of 1.4% on the high side,
whereas a 20T gear will give an error of 3.8% on the low side
(although that might not be a bad thing !).
Mike
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