Re: Speedometer gear question
[Re: Fred_Gilmore]
#1792334
03/31/15 03:40 AM
03/31/15 03:40 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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car in a parking lot with wheels straight ahead. put a paint mark on a rear tire at 8 o'clock. roll car forward till you have two paint marks. tape measure that straight distance which is "rollout". divide Pi into that number to get the actual "diameter" that the speedo will see. there's a chart that shows the correct pinion teeth for tire diameters down to the tenths of an inch. I have it but it wont post as it keeps telling me it needs to be a jpg extension or some nonsense . jack up the car high on the dr side to minimize the fluid loss. be sure to clock the adapter correctly for the number of teeth your pinion going in will have. find that chart (or show me how to post it). You need correct diameter & rear gear ratio
live every 24 hour block of time like it's your last day on earth
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Re: Speedometer gear question
[Re: Fred_Gilmore]
#1792335
03/31/15 11:33 AM
03/31/15 11:33 AM
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Joined: Jan 2003
Posts: 21,072 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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3 MPH and you are worried?They were not that accurate new.Remember its and old mechanical unit not an electronic one like a new car.Rocky
Chrysler Firepower
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Re: Speedometer gear question
[Re: Fred_Gilmore]
#1792336
03/31/15 12:45 PM
03/31/15 12:45 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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if my math is right, a 5 tooth change made a 12 MPH reading change so a 39 (your only choice really other than a gear reduction adapter) so 12 divided by 5 is 2.4 (MPH) so a 39 toother (if there is one and you can locate one) would theoretically slow the speedo another 2.4 MPH & put you very near dead on
live every 24 hour block of time like it's your last day on earth
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Re: Speedometer gear question
[Re: Fred_Gilmore]
#1792337
03/31/15 03:13 PM
03/31/15 03:13 PM
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Joined: Jan 2003
Posts: 25,794 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,794
Rio Linda, CA
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Use the odometer to verify correct speedo pinion, it's direct-geared and won't pick up errors like the speedo does.
The INTERNET, the MISinformation superhighway
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Re: Speedometer gear question
[Re: John_Kunkel]
#1792338
04/01/15 02:01 AM
04/01/15 02:01 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Going off of what master John said, other than a GPS the most accurate test for the odo is the mile markers on the interstate (go five miles) and the most accurate test for the speedo is the temporary roadside lighted digital signs that are set out on occaision. Get the right tooth pinion to get the odo correct THEN if the speedo ain't correct at that point in time right along with it then the speedo head needs to come out & go to a speedometer specialty shop to be recalibrated. EDIT If they ain't equal & I dont want to send out the speedo head then if I can get the right toother in there to get the speedo correct then that is what I prefer (helps with avoiding tickets)
Last edited by RapidRobert; 04/01/15 02:21 AM.
live every 24 hour block of time like it's your last day on earth
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Re: Speedometer gear question
[Re: Sxrxrnr]
#1792340
04/01/15 09:00 AM
04/01/15 09:00 AM
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Joined: May 2005
Posts: 4,727 Florida
BDW
master
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master
Joined: May 2005
Posts: 4,727
Florida
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Quote:
Speedometer - Free - Speed Limit Alert with Map, HUD and GPS Black Box Recorder by Stanislav Dvoychenko https://appsto.re/us/NmhqH.i
Very handy app
Thanks! Love the HUD
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Re: Speedometer gear question
[Re: Fred_Gilmore]
#1792341
04/01/15 11:02 AM
04/01/15 11:02 AM
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Joined: Jan 2003
Posts: 12,078 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,078
Benton, IL.
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We have always used the mile markers on the interstate and the odometer to pick the gear. But be aware that a family member in law enforcement has radared my car several times and the speedo's accuracy is not the same at all speeds. Which is why Mopar offered certified speedos on the cop cars. Of course, the certified speedos came with a correction chart in the glove box because even they weren't accurate at every speed. So I think that you can get the odometer zeroed in, but may have to pick a spot on the speedo to get closer than 3mph while accepting other speeds may still be off.
Master, again and still
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Re: Speedometer gear question
[Re: RapidRobert]
#1792343
04/01/15 12:21 PM
04/01/15 12:21 PM
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Joined: Jan 2003
Posts: 21,072 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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My 65 the speedo is off about 20%.I just adjust to it being off.Its not hard and if it was 3 MPH Id be happy.Like I said new they werent very accurate.Even back then if you were around 5 plus or minus you were doing good.Rocky
Chrysler Firepower
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Re: Speedometer gear question
[Re: Sxrxrnr]
#1792345
04/01/15 11:14 PM
04/01/15 11:14 PM
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Joined: Jan 2003
Posts: 21,072 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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Try and find gears for pre 66 trannys.They are rare and pricey.Ill change trans one day so Im not spending big bucks to get the speed close.It is a lot closer then when it had 4.88s in the rear.Rocky
Last edited by therocks; 04/01/15 11:15 PM.
Chrysler Firepower
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Re: Speedometer gear question
[Re: Bull1tt]
#1792347
04/02/15 10:24 PM
04/02/15 10:24 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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If I can find mine I will take a pic and post the company name. If I was in a rush I'd Google it/ebay & see if anything pops up
live every 24 hour block of time like it's your last day on earth
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Re: Speedometer gear question
[Re: 71birdJ68]
#1792349
04/03/15 10:16 AM
04/03/15 10:16 AM
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Joined: Jan 2003
Posts: 21,072 Niles , Ohio
therocks
oh wait.but hey.lets see.oh yeah.
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oh wait.but hey.lets see.oh yeah.
Joined: Jan 2003
Posts: 21,072
Niles , Ohio
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Imperail Services was making a ratio adapter.They were pricey though.I almost got one from Steve but didnt know what gears I was changing to.3.91s now and either 4.30s or 56s next.Rocky
Chrysler Firepower
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