need help with speedo gears

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inphiniti

Active Member

Mar 15, 2003

412

3

28

Providence, RI

Jun 23, 2008

#1

• Jun 23, 2008

• #1

im going to be runnin 4.10s, but i dont know what size gear tooth i need... some say 23, but some say 23 is a GM product...

what do i successfully need to run 4.10s in an auto?

 

C

cbarr300

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Jun 6, 2006

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goose creek, SC

Jun 23, 2008

#2

• Jun 23, 2008

• #2

get a speedcal and that'll solve all your problems with the speedo

 

Venom351R

Founding Member

Apr 27, 2002

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Jun 23, 2008

#3

• Jun 23, 2008

• #3

http://mustangsunlimited.com/itemdy00.asp?T1=DFM17271J+01

 

Black95GTS

Active Member

Jan 8, 2004

1,644

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Marlborough, MA

Jun 23, 2008

#4

• Jun 23, 2008

• #4

inphiniti said:

im going to be runnin 4.10s, but i dont know what size gear tooth i need... some say 23, but some say 23 is a GM product...

what do i successfully need to run 4.10s in an auto?

Click to expand...

The 23 tooth gear is white, and its a Chrysler gear. Ford gears only go up to compensation for 3.27s (21 tooth). The 23 tooth Chrysler gear will be dead on for a 3.55 gear set. Its close for the 3.73 and still off a bit for the 4.10. It has a reputation for wearing faster due to the chrysler gear not meshing exactly with the Ford gear.

The SpeedCal (or something like it) mentioned above is the only way to get the speedometer and odometer correct and run a 4.10 screw.

Adam

 

Stanger007

Founding Member

Sep 26, 2001

2,015

2

46

Baton Rouge, LA

Jun 23, 2008

#5

• Jun 23, 2008

• #5

Black95GTS said:

The 23 tooth Chrysler gear will be dead on for a 3.55 gear set. Its close for the 3.73 and still off a bit for the 4.10. It has a reputation for wearing faster due to the chrysler gear not meshing exactly with the Ford gear.

Click to expand...

If anyone has a 23tooth and a Ford gear, it would be worthwhile to mic them both and see if the OD of the 23 tooth is larger.

I had seen someone that mounted their 23tooth in a drill then hit it on a piece of sandpaper to bring down the OD and supposedly that made it live longer?

I've got the SpeedCal, actually about to be on my 3rd... first one lasted a good while then started behaving erratically, second one was DOA (read 4x lower than it should despite DIP settings) and third one is in the mail. When they work, they work great. From talking to Dallas Mustang, I am the only person in history to have problems with them, go figure.

Wes

 

I

inphiniti

Active Member

Mar 15, 2003

412

3

28

Providence, RI

Jun 23, 2008

#6

• Jun 23, 2008

• #6

Stanger007 said:

If anyone has a 23tooth and a Ford gear, it would be worthwhile to mic them both and see if the OD of the 23 tooth is larger.

I had seen someone that mounted their 23tooth in a drill then hit it on a piece of sandpaper to bring down the OD and supposedly that made it live longer?

I've got the SpeedCal, actually about to be on my 3rd... first one lasted a good while then started behaving erratically, second one was DOA (read 4x lower than it should despite DIP settings) and third one is in the mail. When they work, they work great. From talking to Dallas Mustang, I am the only person in history to have problems with them, go figure.

Wes

Click to expand...

i hear alot of people have problems with their speedcals... and sometimes i hear the 23 tooth will do the justtice... i might just go that way, who feels like spendin $100 on a speedcal neways... ill just tell my buddy to ride along side of me and tell me how fast im goin

 

Stanger007

Founding Member

Sep 26, 2001

2,015

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46

Baton Rouge, LA

Jun 23, 2008

#7

• Jun 23, 2008

• #7

I'm still split on how having the speedo off affects automatics - particularly the part throttle shifting/locking which is based off MPH/TP - on one hand it seems like it is off initially but that the PCM learns. I have not found out for sure nor found anyone that could properly explain it... wierd eh?

Wes

 

Venom351R

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Apr 27, 2002

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Jun 23, 2008

#8

• Jun 23, 2008

• #8

I also forgot to mention to you that I have a Manual, I know you have an Auto so Im not sure how much difference that will make as far as the speedo gear longevity

 

earleys94gt

Active Member

Aug 31, 2003

1,223

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Ashley, Ohio

Jun 23, 2008

#9

• Jun 23, 2008

• #9

Steeda has a good list too...http://www.steeda.com/products/speedometer_recalibration_gears.php

 

blksn955.o

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Mar 15, 2002

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st.louis mo 314

Jun 23, 2008

#10

• Jun 23, 2008

• #10

Is it possible to mess with the voltage of the VSS to make up for the wrong speedo gear? I have no idea...just asking or is it because there is no real conection with the speedo (guage) and eec?

Could one hook up a resistor of some kind to slow the pulse down?

I am just thinking of a way to maybe make one?

 

Stanger007

Founding Member

Sep 26, 2001

2,015

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46

Baton Rouge, LA

Jun 23, 2008

#11

• Jun 23, 2008

• #11

I got my (third) SpeedCal put in tonite. Ended up putting the replacement in my car, same deal, so put it in another SN95 and it was still not reading correctly. Took it back off and then found out that the DIP switch settings that came with both units are wrong.

I found a better list of the settings here: http://lib.store.yahoo.net/lib/mustangtuning/speedcal.pdf

On the plus side, I can R&R these things in about 10 minutes on an auto now.

Works like a charm...

Wes

 

Black95GTS

Active Member

Jan 8, 2004

1,644

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38

Marlborough, MA

Jun 24, 2008

#12

• Jun 24, 2008

• #12

inphiniti said:

i hear alot of people have problems with their speedcals... and sometimes i hear the 23 tooth will do the justtice... i might just go that way, who feels like spendin $100 on a speedcal neways... ill just tell my buddy to ride along side of me and tell me how fast im goin

Click to expand...

I don't know if you plan on selling that car, but the readings on your odometer are going to be that much of a percent higher. Just something to think about. If I was buying a car and the owner was like "Well there really are 10K less miles, I just didn't want to install the right counter measures when I switched to 4.10s." I'd be like OOOOOOOK next car, have a good one.

In terms of modding the circuit manually, I don't see why this couldn't be done, but it would be an awful lot of work.

Adam

 

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inphiniti

Active Member

Mar 15, 2003

412

3

28

Providence, RI

Jun 24, 2008

#13

• Jun 24, 2008

• #13

yeah the car is paid for, it was a gift so it was not out of pocket... the car isnt going anywhere...

 

94-302-vert

Active Member

Aug 16, 2004

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NE CT

Jun 24, 2008

#14

• Jun 24, 2008

• #14

I vote speed cal too...

 

WhiteCobra95

10 Year Member

May 2, 2006

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Jun 24, 2008

#15

• Jun 24, 2008

• #15

I don't think you can modify the sensor circuit directly since the vehicle speed sensor outputs a PWM signal. The Speedcal is essentially reading these pulses, and then outputting another PWM signal at a different frequency to compensate for the gear change. In short, it's not an analog voltage signal that can be adjusted. (I'm not sure if Ford uses an inductive or hall effect speed sensor? I'll have to check the shop manual and see if it has a supply voltage)

The least expensive but most labor intensive solution is to open up your transmission and change the drive gear along with the driven gear to the older style (late 80's used a different number of drive teeth). Check out the FordRacing Parts catalog. They have half of a page dedicated to speedometer corrections. It gives part numbers for all of their gears, drive and driven. These can all be purchased at the dealer. This opens up the door for way more rear end combinations and if it's done correctly taking tire size into account, could give you the best result. It's not too bad on a MT car - you have to pull the shifter and the tailshaft off of the trans. This information is also available on the fordracingparts web page, but I can't get to it through my work computer since it's a flash site. Maybe someone else can post a link.

- Mike

 

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inphiniti

Active Member

Mar 15, 2003

412

3

28

Providence, RI

Jun 24, 2008

#16

• Jun 24, 2008

• #16

idk, i hear 50/50 on the speedcal... i hear it works... i hear others say it doesnt... i dont know what to do, id like to stay away from it if possible... just not sure what else to do..


what does the speedcal EXACTLY do... and what does the drive gear do?

 

WhiteCobra95

10 Year Member

May 2, 2006

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Jun 25, 2008

#17

• Jun 25, 2008

• #17

Here's the link. Check out the bottom of the page.

http://www.fordracingparts.com/download/charts/142.pdf

 

94-302-vert

Active Member

Aug 16, 2004

1,947

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NE CT

Jun 25, 2008

#18

• Jun 25, 2008

• #18

The speed cal takes the signal input from the exisitng trans output and it sends out a new signal that corrects for the change in gears. This can be almsot infinitely altered if you change gears, tire sizes, etc.

The gear change is cheaper, does not last as long, and is not going to e accurate....

 

WhiteCobra95

10 Year Member

May 2, 2006

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Jun 26, 2008

#19

• Jun 26, 2008

• #19

I read through the FR details last night. It looks like it's not possible to change the drive gear on the AT's, and it comes in too short for 4.10 gears. It looks like the speedcal is the only option for am automatic.

I have a question about the speedcal installation; Do you have to cut any wires to install it, or doesnt it just plug in between the sensor and the harness? That would really be a bummer if you have to dice yoru harness.