speeding ticket, changed gears, needs to be recalibrated!!!

v850mustangluvr · Dec 20, 2004

i got a speeding ticket yesterday, the state trooper said he clock me going 100mph in a 70mph zone, and i told him im not sure how fast i was going because my rearend gears were changed and my speedo isnt accurate!

so he told me i needed to find out my original factory gear and then take it to a tranny shop and have it recalibrated and he said that might make the ticket go away

so what is the original factory gears?

and now i have 3:73 gears so how much do you think my speedo is off....ive tried to see before by going on a sign w/ a built in radar and i always see about a 10-15mph difference...

so i will still be speeding, does anyone have any experience w/ shops and them lieing and saying for me on a paper yeah his speedo was 30 mph off, i need some type of paperwork to take to court...i dont want the shop to get into trouble but how can the court say the shops lieing about the mph!!?? the court dont know crap about that....so do you think i'll be fine, i dont want the court to say, well that sounds wrong, we'll take it to out police car shop and have them check it out

***** then i'll be in trouble and the shop too, maybe im just bugging out for nothing, but where I use to live anything over 20mph speeding is wreckless and i cant get anymore of those!!!!!!!!!!!!!!

thanks for any help!!!!

Tylerb59 · Dec 20, 2004

LOL, ouch.

For the time being you can have a friend pace you at various speeds on the highway. You can take note of these speeds until you have the speedo calibrated.

Michael Yount · Dec 20, 2004

Well - the funny thing is that your speedo should be off the OTHER way; if you went from 2.73's to 3.73's, the speedo should be reading too fast, not too slow.

Here's a link that should help you figure out what's up:

http://www.geocities.com/mgnedell/notchback/tech/speedo.html

87'GTstang · Dec 20, 2004

I have to ask, how in the world did it even remotely feel like 70 mph as opposed to 100?

I had this problem a few years ago except it was with my ranger. I went from the stock 26.4" tire to 31's and when I was clocked as doing 85, The calibration showed to actually be reading 71 mph. Did this clear me - no. But I was reduced for one from doing 20 to 6 over and second my automatic reckless driving charge vanished with it.

5.0 Nostalgia · Dec 20, 2004

Michael Yount said:
Well - the funny thing is that your speedo should be off the OTHER way; if you went from 2.73's to 3.73's, the speedo should be reading too fast, not too slow.

Here's a link that should help you figure out what's up:

http://www.geocities.com/mgnedell/notchback/tech/speedo.html

That's what I was thinking. If you were going 100, your speedo probably said you were going 120. LOL. I don't know how that will get you out of a ticket. For anything above 3.55s in a 90 and up transmission, you need to change the gear inside the transmission to make it accurate. My 91 has 3.55s and needs the 23 tooth gear.

Wil · Dec 20, 2004

happened to me but I wasn't going that fast. Went to court with speedo cal showing that I thought I was going faster then I was caught doing. Well, judge caught that but I guess he felt bad for my effort and lowered the ticket to having falty equipment or somthing like that. It's always worth going to court.

87'GTstang · Dec 20, 2004

Wil said:
It's always worth going to court.

That's my philosophy. By not even showing up or contesting the charge, you are automatically saying that you are completeley guilty as charged and are accepting the full charge. In this case you were doing 100 mph, nothing less and nothing more and that's what will go down on your driving record.

LT1Killa · Dec 20, 2004

Didn't you notice that you were flying by cars going thirty mph faster than them?? Something smells fishy here. I think you were out there hot roddin it and got caught and this speedo excuse is the best you could come up with.

And yes, the speedo will read fast, not slow.

83GT289 · Dec 20, 2004

what you need to do is go to a shop and get it checked. They won't fix it but they will give you a paper to take to court saying your speedo is off. You can try for "improper equipment". It doesn't really matter wich way the speedo was off just that it isn't accurate.

J.

ratrapp · Dec 20, 2004

i got clocked at 101 in a 55.i told them i knew i was speeding,just not by how much.i went to court and plead guilty and took my punishment.they took my license for 90 days and 4 days in jail.you can try to get it calibrated but there going to say you knew you were speeding.i used to calibrate speedometers and you won't believe the storys you here or propositions you get to lie about the speedometers.

tendo · Dec 20, 2004

LOL! I have simliar problem in my 84. When it says Im going 75 my buddy next to me was going 60 and at 65 I was going 50. That is of course with 3.73s in and I agree that this guy was just hot roding around and got busted now needs an excuse. I just watch my tach closely and the traffic around. Safe.

87'GTstang · Dec 20, 2004

Seriously, it's $10-$15 for the speedometer gear, why the pass on it?

Wil · Dec 20, 2004

87'GTstang said:
Seriously, it's $10-$15 for the speedometer gear, why the pass on it?

how hard is it to install, I have 4.10's an my speedo is waaaay off.

5.0 Nostalgia · Dec 20, 2004

Wil said:
how hard is it to install, I have 4.10's an my speedo is waaaay off.

Couldn't be easier. Just crawl under the car and pull the connection out of the back of the tailshaft. It is held in place by a single bolt and a C shaped bracket. After pulling the cable out, you will see the gear on the end of it. A c clip holds it in. Take the clip out and put the new gear in.

chaos254 · Dec 20, 2004

hmmm my speedometer reads low. I have 2.73's and when my speedo reads 70 I'm really doing like 85. I've verified this by pacing a friend and checking online with one of those calculators. I tried replacing the external gear but it was the same exact one as stock. The guy who owned the tranny I swapped it must have changed the internal one. I still dont understand why it reads slower though....any suggestions??

trbkrb · Dec 20, 2004

5.0 Nostalgia said:
Couldn't be easier. Just crawl under the car and pull the connection out of the back of the tailshaft. It is held in place by a single bolt and a C shaped bracket. After pulling the cable out, you will see the gear on the end of it. A c clip holds it in. Take the clip out and put the new gear in.

Still won't make it correct, but it will be closer. If he has the 8 tooth drive gear in the tranny(the gear on the output shaft, stock on 90+ T5s is 8 tooth), he would have to change to a 6 tooth drive gear and get the closest tooth speedo cable gear to make it more accurate. 19 tooth is probably it. Check it here:

http://www.hanlonmotorsports.com/t5speedo.asp

To make it right on you need this: http://www.gaugeguys.com/ratioadapt.htm

I have 3.73s and run a 21 tooth gear, and mine is STILL reading about 4-5 MPH fast at 60MPH.

Good luck!

notch4949 · Dec 20, 2004

trbkrb · Dec 20, 2004

chaos254 said:
hmmm my speedometer reads low. I have 2.73's and when my speedo reads 70 I'm really doing like 85. I've verified this by pacing a friend and checking online with one of those calculators. I tried replacing the external gear but it was the same exact one as stock. The guy who owned the tranny I swapped it must have changed the internal one. I still dont understand why it reads slower though....any suggestions??

If he did change the internal gear, the speedometer is reading slower with the driven gear you have, if you got the one for the 8 tooth internal gear. Look at the Hanlon chart I posed above and see what gear it says for a 7 tooth internal gear with your rear end gears. It will probably be one with a couple fewer teeth and that will turn the cable a bit faster.

jrichker · Dec 20, 2004

Check to see if there is a speedometer shop in your area. If there is, ask about the Stewart-Warner speedometer gearbox. I believe it is either a 777 Series Drive Joint Kits and Parts or 666 Series Drive Joint Kits and Parts. It is a small gear box that fits between the speedo pickup gear on the transmission and the speedometer. It has quick change gears that allow you to choose almost any tire size and rear end gear ratio you want. This will allow you to get the accuracy with within 1%-3%. The drawback is that it isn't cheap.

See http://www.gaugeguys.com/ratioadapt.htm for more info.

5.0 Nostalgia · Dec 20, 2004

trbkrb said:
Still won't make it correct, but it will be closer. If he has the 8 tooth drive gear in the tranny(the gear on the output shaft, stock on 90+ T5s is 8 tooth), he would have to change to a 6 tooth drive gear and get the closest tooth speedo cable gear to make it more accurate. 19 tooth is probably it. Check it here:

http://www.hanlonmotorsports.com/t5speedo.asp

To make it right on you need this: http://www.gaugeguys.com/ratioadapt.htm

I have 3.73s and run a 21 tooth gear, and mine is STILL reading about 4-5 MPH fast at 60MPH.

Good luck!

Yeah, I am aware of that. As I said in the other post, I need a 23 tooth to make the 3.55s accurate in my 91. But the drive gear is a lot harder to change than the driven gear. I wouldn't bother with it unless I was taking the transmission out. That 2nd link was pretty cool.

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