Ford Mustang Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
What I deem as "important" information, I put in red.

Background Information about my car:
-1997 Ford Mustang Convertible
-6 Cyl
-Automatic
-3.8L
-"Normal" Tires. Got them balanced/replaced 4 months prior to this incident.

Story:
Yesterday (or today), I decided to go on a brief "road-trip" with my girlfriend. It was going to be 3-4 hours there, and 3-4 hours back. The total time would then be 6-8 hours of driving in this Mustang.

We left at 3:00am; and so there was hardly any other cars (specifically, police) on the way down to my destination. After arriving and spending an hour sight-seeing and relaxing, we left around 8 or 9am to drive back.

I don't normally speed, but I wanted to show my girlfriend what the governor on my Mustang felt like (odd, yes). From past experience, my speedometer has NEVER been able to reach 100+ mph. Whenever the speedometer reached 100mph, the governor kicked in and stopped my acceleration. I know this to be accurate as I tested it several times before this moment with my girlfriend.

Being unlucky, a cop was there to greet me on the highway exactly when I was trying to show my girlfriend the governor. However, my governor didn't kick in (so I know I didn't reach 100mph according to my speedometer, FOR SURE), and my speedometer read around 95-97 mph when I glanced at it.

The cop did end up catching my speed, and told me he clocked me at 111mph (he showed me the radar gun). I told him that's not possible and that my car has a governor set at 100mph. I couldn't really argue with his radar gun, however, and I thought it was odd since my car has NEVER gone higher than 100... as it can't.

Around thirty minutes later I'm on a 70mph speed limit highway. I look at my speedometer, I'm going 76-78 MPH. I see a cop ahead, and slow down just in case even though I know I am fine as I wasn't speeding (I'm really not a huge speeder). He ends up pulling me over.

He (the cop) tells me that he clocked me at 86mph. I knew for a FACT that I was not going that fast, as I had my auto-cruise set on 76-78. I even looked at the speedometer as the cop signaled his lights and it read 76-78, before I braked.

I told the cop that my speedometer MUST be off. He then told me that if I took it to a shop and they saw that the speedometer was off; then the court would excuse that ticket.

The third ticket I received was basically the same scenario, and also happening within the same hour (I was fed up with cops at this point).

After that, I had my girlfriend take out her GPS and tell me what speed it said I was going. When I was going 65 MPH, according to my Speedometer, her GPS said I was going 75-78MPH. The higher my speedometer went, the higher the error was. I KNOW something is wrong with it.

Question:
Basically, I took my Mustang to the Ford Dealership, and they told me they checked with their computers/equipment and could find nothing wrong with my speedometer. What should I do at this point? I KNOW there is something with it, no doubt in my mind. Is there something I should tell them to check specifically? Who should I take it to? I live in Overland Park, Kansas. I did get the tickets in Missouri though.

Any information would be greatly appreciated. I really hope to resolve this, even if for future tickets as well.
 

·
Registered
Joined
·
368 Posts
110 is when the thing should kick in. Maybe someone put gears in your car. That might be why your speed would be off.
 

·
Registered
Joined
·
2,004 Posts
Jesus.
I'd just quit driving if I were you.
No, his state needs him to keep getting tickets so he can keep paying them :smartass:

But on another note.... how did you get out of the 111mph traffic stop? Every cop I know would have taken you to jail. And I know quite a few cops, so I want to hear your story :bigthumbsup
 

·
Registered
Joined
·
1,657 Posts
I would remove the speedometer sender and inspect the plastic gear on it to see if the teeth are worn and are slipping.

It is common for that small gear to wear.
 

·
Registered
Joined
·
2,004 Posts
^ I thought the last year with a speedometer gear was the 1995 Mustangs....?
 

·
Registered
Joined
·
1,657 Posts
^ I thought the last year with a speedometer gear was the 1995 Mustangs....?
93 was the last year with a speedometer cable.
98 was the last year with a speedometer gear.
The gear drives an elecronic sender (VSS) on the side of the transmission.
 

·
Banned
Joined
·
12,436 Posts
c'mon man, I could see the 3rd one, but the first two? One; Guilty and you know it, 2: you would have been passing almost every other car on the road and you would have to be drunk to not have a feel for 85,mph compared to 75
You may be lucky to be driving after your court date, wait until your insurance gets wind of this, if I was you, I'd hire a lawyer
 

·
Registered
Joined
·
6,859 Posts
Your speedometer is off by about 24-27% based upon the GPS. Which means when the speedo says 100MPH, you are actually doing 120+.

If a lower rear end gear were installed and the speedometer not corrected, then the speedometer would read high (not slower than true speed).

Now if there were lower gears installed, the speedometer corrected and then stock gears re-installed, that could make the speedometer read low. But this seems far fetched.

Is it possible that a 160 MPH GT dash overlay has been installed on top of the V6 cluster? This would account for the speedo reading 25% in error (very close to the amount the speedo is off). The dealer is unlikely to catch a "mod" such as this.

What is the top speed on your cluster?

Larger tires would make the speedo read low.

I just don't see this being a stripped VSS gear gear problem. The results are too "neat". A stripped gear would have a jumpy speedometer. With an automatic, this would affect the transmission's shifting.

Also assuming there isn't a "SpeedCal" or other mod to your car.
 

·
Registered
Joined
·
391 Posts
Jesus Christ I thought I had a problem hahahaha
 

·
Registered
Joined
·
2,905 Posts
I don't know the governor has 'feel"

Probably taller tires.

You might have a local shop that specialized in speedos where they will put it on the dyno and give you a printout of the accuracy for around $20.
 

·
Registered
Joined
·
1,657 Posts
IYou might have a local shop that specialized in speedos where they will put it on the dyno and give you a printout of the accuracy for around $20.
This is what you need for court. If you can PROVE that it is off AND that the problem has been corrected, you will have a LOT better outcome in your court cases.
 
1 - 14 of 14 Posts
Top