How do I verify the speedo after gears?
03-08-2008, 12:11 PM
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How do I verify the speedo after gears? Here's the deal. I know exactly what ratio I have. 3.73, since I put the ring and pinion in myself. The car is a 2000 TransAm A4.
I had the car tuned by one of the best tuners on the east coast. But, I'm not sure the mph on the speedo is correct. I was told they set eveything correct for 3.73. They've offered to put it on the dyno to verify. Before I go this route, I wanted to verify for myself. For Corvettes, you can put the car in 3rd and at 75mph, divide RPM's by 1000 to tell your ratio. For the F-bodies, what's the speed to you have to go for this trick.
What I'm trying to do is verify that my speedo is set correctly. Any other suggestions? Last resort is to pace a friend's car on the highway.
Thanks.
I had the car tuned by one of the best tuners on the east coast. But, I'm not sure the mph on the speedo is correct. I was told they set eveything correct for 3.73. They've offered to put it on the dyno to verify. Before I go this route, I wanted to verify for myself. For Corvettes, you can put the car in 3rd and at 75mph, divide RPM's by 1000 to tell your ratio. For the F-bodies, what's the speed to you have to go for this trick.
What I'm trying to do is verify that my speedo is set correctly. Any other suggestions? Last resort is to pace a friend's car on the highway.
Thanks.
03-08-2008, 12:50 PM
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Get your girlfriend in her little Kia Rio out on the highway and get two Scooby Do walkie talkies, then have her pace you side by side. You can then talk dirty to her while she records her speedo and relays it back to you.
Or you can wiz past a state patrol on the highway at 6,000 rpm and see how fast your clocked at when you get pulled over.
Or you can wiz past a state patrol on the highway at 6,000 rpm and see how fast your clocked at when you get pulled over.
03-08-2008, 01:30 PM
#3
This is what i did, get a stop watch, and a friend. Go out on the highway or anywhere with mile markers. Set you cruise at what is 60mph then soon as you pass a mile marker hit the timer, and when you get to the next one it should be approximately 1 minute. This what i did to get my car as close as possible when i had my gears installed with the diablo handheld tuner.
03-08-2008, 02:44 PM
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Get your girlfriend in her little Kia Rio out on the highway and get two Scooby Do walkie talkies, then have her pace you side by side. You can then talk dirty to her while she records her speedo and relays it back to you.
Or you can wiz past a state patrol on the highway at 6,000 rpm and see how fast your clocked at when you get pulled over.
Or you can wiz past a state patrol on the highway at 6,000 rpm and see how fast your clocked at when you get pulled over.
03-08-2008, 02:53 PM
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Go out for a drive and look at what gear your in, speed, and rpm. Then verify here.
http://www.f-body.org/gears/
http://www.f-body.org/gears/
Seems like pacing it is the only option.
03-08-2008, 03:14 PM
#7
Thanks for the link......problem is I don't think those calculators are accuate. Theoretically, they are accurate, but real life is somewhat different. I guarantee that no one will see those numbers exactly match up. I think the problem lies in the fact that the tire diameter is lower, due to the weight of the car. It squishes out some, reducing effective diameter.
Seems like pacing it is the only option.
Seems like pacing it is the only option.
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03-08-2008, 03:41 PM
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Thanks for the link......problem is I don't think those calculators are accuate. Theoretically, they are accurate, but real life is somewhat different. I guarantee that no one will see those numbers exactly match up. I think the problem lies in the fact that the tire diameter is lower, due to the weight of the car. It squishes out some, reducing effective diameter.
Seems like pacing it is the only option.
Seems like pacing it is the only option.
Even if the tire sag is like a 1/4 inch it only effects the gear calculator my one mile an hour.
As long as your tires inflated to the specified amount I would at least compare your results with the gear calculator
03-09-2008, 06:00 AM
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GPS unit. That is what was used to find out how fast I'm going. Long story short, I got pulled over for doing 70+ in a 65. Needless to say, I was like WTF. Buddy pulled out his GPS unit and rode with me in the car and it reported my MPH. I was off by +4MPH. Not good when you have a cop behind ya pacing you for 3.5 miles.
BTW, My speedo was right on 70MPH when the cop nailed me. Now, Of course i adjust my speed to compensate for this discrepancy (66/67 on the speedo) for 70MPH with 3.73's. Ya, I hate it, but i will get it fixed once get through my court date.
I did try to have the dealer fix it, but all they said was it's within spec. O well.
BTW, My speedo was right on 70MPH when the cop nailed me. Now, Of course i adjust my speed to compensate for this discrepancy (66/67 on the speedo) for 70MPH with 3.73's. Ya, I hate it, but i will get it fixed once get through my court date.
I did try to have the dealer fix it, but all they said was it's within spec. O well.
Last edited by MYTFASTSS; 03-09-2008 at 06:09 AM.
05-13-2008, 08:36 PM
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GPS unit. That is what was used to find out how fast I'm going. Long story short, I got pulled over for doing 70+ in a 65. Needless to say, I was like WTF. Buddy pulled out his GPS unit and rode with me in the car and it reported my MPH. I was off by +4MPH. Not good when you have a cop behind ya pacing you for 3.5 miles.
BTW, My speedo was right on 70MPH when the cop nailed me. Now, Of course i adjust my speed to compensate for this discrepancy (66/67 on the speedo) for 70MPH with 3.73's. Ya, I hate it, but i will get it fixed once get through my court date.
I did try to have the dealer fix it, but all they said was it's within spec. O well.
BTW, My speedo was right on 70MPH when the cop nailed me. Now, Of course i adjust my speed to compensate for this discrepancy (66/67 on the speedo) for 70MPH with 3.73's. Ya, I hate it, but i will get it fixed once get through my court date.
I did try to have the dealer fix it, but all they said was it's within spec. O well.
Thanks!
05-14-2008, 02:08 AM
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05-14-2008, 03:21 PM
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So, if you have 3.73's, you should be turning 3730 RPM (give or take
)
05-15-2008, 07:41 PM
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All I did was go by one of those signs that shows your real speed and compared to my speedo. With 3.73s I was only like a 1/2 a mile an hour off after I recalibrated. Not enough to worry.