need help with speedo gears
- Thread starter inphiniti
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Black95GTS
Active Member
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
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
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 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
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
Wes
earleys94gt
Active Member
blksn955.o
Founding Member
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?
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
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
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
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
94-302-vert
Active Member
WhiteCobra95
10 Year Member
- May 2, 2006
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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
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
WhiteCobra95
10 Year Member
- May 2, 2006
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Here's the link. Check out the bottom of the page.
http://www.fordracingparts.com/download/charts/142.pdf
http://www.fordracingparts.com/download/charts/142.pdf
94-302-vert
Active Member
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....
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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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.
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.
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