Making myself a 145MPH speedometer.

ricardoa1

Registered User
I will be making myself a 145MPH speedo during the next few cold winter days. I know my car is governed with the darn Auto but Im hoping that will change in the future so Ill be doing this mod without spending a fortune.


You too can have a 145MPH speedo for very cheap money using your exsisting 120MPH speedo. Its not new and im def not the innovator here, but bringing things back up can be new news to the newbies who are paying over $100bux to get a cool 145MPH gauge.


There are several people selling 145MPH faces.

The ones I like the most are the reverse glow ones I have them in my 94SC and they look super cool at night. They are somewhat expensive though.

http://www.streetracerparts.com/Ford_Thunderbird_SC_1994_1995_Halo_Style_Illumiglo_p/srp-0129.htm

SRP-0129-2.jpg


There is also someone on ebay selling a kit that has all the years included these are your plain old white face with the green numbers. I saw them last night going for about $22 bux. Unsure on the quality but I am sure it will get the job done.

Another source is the old school NRauto.com very high quality. I used to have these, and they are now affordable they use to be over $100 dollars.

http://www.nrauto.com/sub_index.asp?spage=Gauges

3312.jpg


Another source is the guy from TCCOA.

Or last find your self selling a broken 145MPH speedo and steal the face of it and use it on your 120MPH speedo. This will give you the black with eggshell texture that the factory gauge has.


Then read this article http://www.sccoa.com/faq/SpeedometerConversions.pdf

and go to radio shack and get some resistors.

Last have fun :) Ill try to document my progress.
 
Last edited:
hmmmmm, with my old 93 auto I had, it had no modifications, and there was no governer....I remember pegging the speedo many a times, and holding it for at least another 30 seconds before I had to let off due to the horrible loud yell of the upshift light screaming at me.....maybe certain years are different???
 
hmmmmm, with my old 93 auto I had, it had no modifications, and there was no governer....I remember pegging the speedo many a times, and holding it for at least another 30 seconds before I had to let off due to the horrible loud yell of the upshift light screaming at me.....maybe certain years are different???

mine also i have pegged the speed o on my 92 i know because i also did this mod!
 
I beleive what he is saying is the car wont peg the 145 on an AOD for they are governed prior to that speed.

-Tim
 
After reading the article, I still couldnt figure out which resistor value is used to come up with a 145 mph value on a 120 speedo. The 120's are easy to come by and I have 2 145's here that have non functioning odometers .. want to switch out the faces to some good units.

- Dan
 
After reading the article, I still couldnt figure out which resistor value is used to come up with a 145 mph value on a 120 speedo. The 120's are easy to come by and I have 2 145's here that have non functioning odometers .. want to switch out the faces to some good units.

- Dan

Have you replaced the gears in the units or at least inspected them to see if this is what might be causing the problem?

-Tim
 
Have you replaced the gears in the units or at least inspected them to see if this is what might be causing the problem?

-Tim


Of course, gears are great .. replaced motors, circuit boards, etc etc .. still only works Intermittently - it seems like it works some of the time if I press the Trip meter reset button, IDK .. something sticking, something loose, something broken.

- Dan
 
You can cheat and wait till I get the correct resistors. But there are two types of 120 speedos so one set of resistors will not work on the other. I think the Original author is just covering his bases. Use a GPS nav unit to get the correct speed.
 
I'll wait, just keep us informed. :D Dont have a GPS and have plenty of time while the SC is down ( again .. :rolleyes: )

- Dan
 
Of course, gears are great .. replaced motors, circuit boards, etc etc .. still only works Intermittently - it seems like it works some of the time if I press the Trip meter reset button, IDK .. something sticking, something loose, something broken.

- Dan

I was wondering for I have a 93 SC - I replaced the Speedometer head with a known good one...it worked for 128 miles and now is dead again. I'm starting to think it might be the actual cluster itself causing the issues at this point.

I have several clusters laying around I can try to swap out but who knows.

Sorry to get off topic Rico.

I have like 4 93 SC speedoheads laying around, wanna do em for me :D

-Tim
 
I tried using the speedo from the parts car I had and I went out and nothing happened. I reluctantly did the mod to the factory speedo that was in my 90SC. This one seems to work. I managed to break the needle off this one too. I would not use kitchen forks to get this thing off. Thank god for a wonderful member that hooked me up with not only one but two needles. ;)

Well I went out with the working speedo, Mine is the early one with the 65MPH on the 12oclock spot. I have been unable to borrow a navigation unit to verify, but in third gear with the direct drive AOD my car cruised at 2500RPMS at around 56-57 MPH, with the 120 speedo. With the new face and attempting the same, I needed to use one....330-Ohm resistor and one 47-Ohm in series. So a total of 377 Ohms. I think I am there I want to confirm before putting it all back together. Since you can only use two resistors in series according to the original author those two combinations are the only ones to get it to read accurately for the 145MPH face. One could try moving the needle a tad bit up to compensate too. Ill post some pics later.
 
Last edited:
OK I got a GPS unit to double check and it seems that the RPM way works well the Speedo was off about 2-3 MPH I cannot find a set of resistors to compensate so I will be moving the needle up and instead of starting at 0 it will start 2-3 mph. So this does work. I just have to put things back together. :(
 
update- how to get resistor value needed

Get a variable resistor that has a decent range and temporarily hook it into the cluster(where you would hook in the resistors) on long leads.
Then you can make adjustments as you need to.
When you have it at the correct value, pull it out and read the value with an ohm meter.
Assemble the resistors to match the value, and install.
If you can find a variable resistor (the kind that can be mounted on a circuit board), that can handle the current mount it on the rear of the cluster with epoxy or a good glue. If you can mount the pot where the adjustment screw can be accessed from the front of the cluster, drill a small hole in the cluster face and bezel to allow future adjustment without ripping the dash apart (ie changing gears or tire size).
MikeH
 
ordering new gauge faces ..

Talked to Scott, desided to get a set of Black Powerlines, blue illum. and 145 speedo. look nice on the computer, wife liked them also.
MikeH
 
There's a much simpler way to do this than running an inline resistor to the speedo motor, at least with the 91-96 speedos. The resistor at the edge of the board right next to the microchip is all that needs to be changed(I don't remember the value for the 145 though). The odometer board also uses a larger capacitor on the 145 vs. the 120, though I haven't reverse engineered the whole circuit to figure out why.
 
Talked to Scott, desided to get a set of Black Powerlines, blue illum. and 145 speedo. look nice on the computer, wife liked them also.
MikeH

Received my new gauge faces from Scott today. They look very nice. Now I have to pull one of the clusters out to install.
MikeH
 

Attachments

  • scott's new faces.jpg
    scott's new faces.jpg
    46.6 KB · Views: 41
Last edited:
Back
Top