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#1 |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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My truck's interior is not finished yet so I don't drive it much but it seemed to me that the miles were not adding up on the odometer very fast but I didn't give it much thought till I checked it with my gps. I wrote down my mileage and drove into town. My gps said I went 5.1 miles and my truck said 2.2. My speedometer is 4 MPH slow- It makes no difference whether I drive 10 or 60 i'm going 4 MPH faster than it's showing, but that won't throw my odometer off that far will it? I tried using the search but couldn't find anything and I don't know how these odometers work- can someone please help me out here?
BTW, my guages are rebuilt white face ones from the guy on ebay. I don't know what it was like before I tore my truck apart-I never checked. My truck is a 72 Chevy 4x4 3.73 350/350 on 15x8 ralley wheels 31x11.50's
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#2 |
Senior Member
![]() Join Date: Jul 2010
Location: Race City U.S.A.
Posts: 1,014
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Re: Odometer Not Even Close
You actually have a good problem. I remember a while back, I had a lease vehicle. I think I got 12,000 mile allowance. I bought some wheels and tires that were a smaller diameter than stock cause I lowered it a bunch. Well, the smaller tire made the speedometer 5 mph faster which of course put more miles on it than it should have. I really kicked myself for that one.
Your case is the opposite of mine. Yours is slower and it is putting less miles on it. I understand you probably just want it to be correct, I would want the same for my C10. So, you can either deal with it, or you can change out the speedometer gear. I can't tell you which one you will need as it will depend on your rear end gear as well. I would start with counting the teeth on your current gear and going from there. Do an EBAY search for C10 NOS and a bunch of them will be listed there. You can also search 350 speedometer gear and there are a bunch more. Good luck!
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Board Member #87725 My build thread... http://67-72chevytrucks.com/vboard/s...d.php?t=813848 |
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#3 |
Registered User
Join Date: Aug 2010
Location: San Diego, CA
Posts: 128
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Re: Odometer Not Even Close
Changing the speedo gear at the transmission is easy but it will affect both the speedometer and the odometer. I don't see how the speedo can be pretty close (although 4 MPH at 40 is still 10% off) but the miles read less than half of what they should. If the wheels or in the odometer have wear it may be that they are not advancing the way they should.
Does your speedo needle hold steady, or does it bounce some when you are at a steady speed? I had a bad odometer and the gears on the number wheels would bind up and not turn correctly, but that made the speedo needle bounce whenever the odometer wheels would stick. |
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#4 | |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
Quote:
Good thought. My needle doesn't bounce a lot but when I speed up the needle will hesitate just a tiny bit then jump quickly to catch up and then then it bounces a little as it settles down- it's kinda like it sticks just a bit. I think it only does it when I speed up quickly but I can't remember for sure. Thanks for the comments all. I don't have time to look at anything right now- gotta get to work. Maybe at lunch I can click on that link.
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#5 |
Who's got steelies?
![]() Join Date: Feb 2006
Location: Morrison, Oklahoma
Posts: 1,026
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Re: Odometer Not Even Close
Go here: speedometer world they have a chart to help you figure out what speedometer gear combo in the transmission you need based on your tire size & rear axle ratio. The odometer part is pretty well fixed in the speedometer head, 1000 revolutions of the speedometer cable is 1 mile. The actual indicated speed is adjustable for calibration purposes, but doing any adjusting will be worthless if the odometer is off.
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#6 | |
Senior Member
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Location: New Madison, Ohio
Posts: 21,365
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Re: Odometer Not Even Close
Quote:
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A husband can be right...or...A husband can be happy. ![]() 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. ![]() 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc ![]() ![]() JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder! |
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#7 |
Registered User
Join Date: Jun 2010
Location: Parkville, MD
Posts: 163
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Re: Odometer Not Even Close
I'm hardly an expert, but logic tells me that if at any speed, you're always off by 4mph, then how can it be the speedo gear/tires/rear end, etc? Changing those would make the speed off by a percentage, which means that the faster you went, the more the mph would be off - not a constant 4 mph. Instead, I would think that the gauge is not properly set at zero, but again, I'm no expert.
Interested to see what the opinions are. |
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#8 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,961
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Re: Odometer Not Even Close
I believe you are correct Patrick, i.e. it's a proportional percentage. For example, on my dd (an 01 chevy truck) I have slightly taller tires than stock - the result, as expected, is that I'm "showing" less than I'm "going"... NOT good if you're trying to avoid tickets. Anyhoo, to the point about percentage amount off - when I'm going 50-55, it's only off by about 3-4 mph, when I'm up at 75 mph, it's off by 5-6 mph (both on the slow side).
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#9 |
Registered User
![]() Join Date: Mar 2011
Location: Disneyland, CA
Posts: 486
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Re: Odometer Not Even Close
Yes it's proportional. Before I fixed it, mine was 10% over so when it read 40 I was doing 36 when it read 70 I was doing 63. At least according to my GPS.
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#10 |
Registered User
![]() Join Date: Oct 2009
Location: Phoenix, AZ
Posts: 475
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Re: Odometer Not Even Close
I chased around a similar problem. Found that 2 teeth on the speedo driven gear in the transmission were worn down to almost nothing. My speedo was also reading 10% low because I have 31" tires, so I replaced both gears in the transmission and solved all my issues - rock steady needle, accurate to 1 mph at 60, and correct odometer reading.
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1971 C10 Longbed, 350/TH350 |
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#11 | |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
Quote:
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#12 |
425hp409
![]() Join Date: Oct 2008
Location: Prosper Texas
Posts: 841
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Re: Odometer Not Even Close
The odometer is a direct mechanical drive off of the speedometer cable. You can change the gears in your transmission, or get a reducer adapter to correct this, but any change you make with the odometer will also change what the speedometer reads by the same proportional amount. The problem you have is twofold. 1. The speedometer gears are wrong for your truck with the gearing you have. 2. The speedometer is way off of calibration. If you change your odometer to read correct, the speedo will be really way off. You will not be able to make both of them read correctly with the existing speedometer that you have unless you take the speedometer out and have it calibrated magnetically at a speedo repair shop.
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Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette |
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#13 |
Senior Member
![]() Join Date: Jun 2010
Location: Orlando, Florida
Posts: 2,508
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Re: Odometer Not Even Close
The good news is that once you fix it your gas mileage will go up significantly!
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71 Chevy C10 Shortbed Stepside. LT1 with 4l60E. Just got back from painter, in assembly now. |
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#14 | |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
Quote:
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#15 |
State of Confusion!
![]() ![]() Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,923
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Re: Odometer Not Even Close
I think you have a mechanical issue in your speed head, mainly the odometer. probably a wore gear in there. I think before I would messing with the gears to get the speed accurate, I would tray gauge head to see if your odometer acts correctly (or at least closer). Then I would dive into getting the speedometer accurate.
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Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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#16 | |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
Quote:
Makes sense cause I drove it to work today and I'm noticing that the odometer is not consistant at all- last night driving home it was turning over just about dead on with the gps. Like 1-2 tenths off in a couple miles. and this morn it was real close part of the time but when I got to work my gps said 5.6 and the truck said 3.2. So I drove half a mile more than in my first post but my truck thought it was a mile more.
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#17 |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
On second thought, are you saying I should replace the gauge itself? I have "new" guages from the guy on ebay but I guess that doesn't garentee mine's not bad.
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#18 | |
State of Confusion!
![]() ![]() Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,923
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Re: Odometer Not Even Close
Quote:
If you have another guage I would try it just to see if you get a different reading.
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Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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#19 |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
I was reading the ad on ebay and sounds like the guy uses original parts for the clusters he sells so could be mine is wore out. He says he'll replace any defective parts for free but I'd like to know for sure if that's the problem. I don't have my old cluster any more but maybe I can ask around and get one. I sprained my ankle really bad last night so could be a while till I'm going again
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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#20 |
Registered User
![]() Join Date: Apr 2007
Location: Foster Rhode Island
Posts: 1,176
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Re: Odometer Not Even Close
Just because its new dosn't mean it can't be broke.
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#21 |
Who's got steelies?
![]() Join Date: Feb 2006
Location: Morrison, Oklahoma
Posts: 1,026
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Re: Odometer Not Even Close
OK, do this then:
find something that you can use as a handle like an allen wrench & put it in the back where the speedo cable goes on the speedo. Turn it 100 turns. You've got to turn it forwards, because there is a ratchet-like device in the odometer reel that prevents miles from being subtracted in reverse (remember Farris Beuller's Day Off?) The odometer should move 1/10th of a mile. You could do this 10 times if you've got the patience and every gear in the thing would have gone round at least 1 turn & it would be 1 mile from where you started. Anyway, if it passes that, get a short piece of old speedo cable or something that will let you spin it with a drill motor without damaging the square hole that the speedo cable goes in. I like using a small flat blade screwdriver bit. Run it at about 60 mph and watch the odometer. It should do one mile in one minute. If the odometer pauses or does less than 1 mile, somethings wrong. If everything checks out OK it your speedo cable or speedo gears in the transmission.
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#22 | |
Under Construction
Join Date: Sep 2009
Location: Summersville MO
Posts: 176
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Re: Odometer Not Even Close
Quote:
Thanks a lot for your advice.
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72 chevy 4x4-my project 67-72chevytrucks.com/vboard/showthread.php?t=368210 94 Nissan 4x4-Daily Driver and off road beater 03 Saab 9-3 -tripper 90 Polaris Trail Boss- 2 Stroker |
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