Anyone know how to Recalibrate a speedometer?

Discussion in 'Green Room' started by bush dogg, Mar 18, 2007.

  1. bush dogg

    bush dogg OSNN Senior Addict Political User

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    I have a 1983 Chevy crew cab dually the speedometer quit working on. I’ve just got another speedometer and want to set the odometer to match my old one so the question... Is there anyone that knows how to recalibrate the odometer on this truck.

    I’m not talking about setting it back; I need to set the miles ahead by about 63,000 to match what I had when mine quit working a few weeks ago.
     
  2. Perris Calderon

    Perris Calderon Moderator Staff Member Political User

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    I don't think you can do it without running it out, they've got some kind of tampering mechanism to detect changes in the odometer

    I'm no expert though
     
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  3. American Zombie

    American Zombie Moderator Staff Member Political User

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    You can either replace the odometer on new speedometer with the odometer on old speedometer or take new odometer apart and adjust it.

    Would be easiest to just replace new with old.

    The following may not pertain to your situation exactly but will give you an idea of how to proceed.

    Changing the Odometer
     
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  4. Grandmaster

    Grandmaster Electronica Addict Political User Folding Team

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    gonaads is the resident car expert, he'll prolly have his 2 cents to add :)
     
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  5. bush dogg

    bush dogg OSNN Senior Addict Political User

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    Yep that’s what I thought, I looked at it for just a second then went on to something else thinking I would post this and someone might have a slick plan.

    When it gets light out I will take a look and see what it involves replacing the odometer’s “I just might have made it harder that it was sitting there thinking about”.

    I will await his arrival, he just might have a choice of words and hand movements that will accomplish this?

    It’s a diesel 6.5L I put in that truck a few years back and yesterday I had to replace the radiator “has transmission and engine oil cooler lines that connect to the radiator” along with all the heater/bypass hoses so I’ll admit all day long I was miraculously remembering sweet words I hadn’t used in more that 25 years!
     
  6. Perris Calderon

    Perris Calderon Moderator Staff Member Political User

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    from what I remember, there is a plastic membrane that breaks when you play with the wheels and they will no longer turn correctly once that seal is broken

    I think you can put something in place of that seal and it will work fine but it will be obvious you tampered

    this is actually legal if you inform the next buyer the odometer was tampered with and you get documentation that they know it
     
  7. rushm001

    rushm001 In the beginning...... Political User

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    I personally wouldn't bother. If you do put it forward it will just make the mileage figures look like thay have been clocked. When the time comes to sell it you just have to say that the actual mileage is 63k ish more than it is shown, tis better than trying to explain why it looks clocked. :)
     
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  8. bush dogg

    bush dogg OSNN Senior Addict Political User

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    Yep I’m not sure what’s in there but I heard a lot of different features to divert you from doing this on your own.
    (I could take it to a speedometer shop here in town but for two reasons)

    1-------I don’t really want to pay just over $200.00 and drive an hour to get there. (Unless there’s no other way)
    2-------I’m real particular about this truck and with its age if something else gets broke in the process of fixing the speedometer I would rather I was the one that broke it so I could fix it right while in there. It seems anymore here in town most specialty shops that you wouldn’t visit frequently that have another parts break in the process of fixing something will peace it back together if they think there going to be responsible for it.



    According to Federal Law “most states also have this law now” you have to include a sticker on the left door post with the old mileage on it also.


    Your right and I have thought hard about just putting the new speedometer in as it is and letting it be that way, But I just can’t bring myself to be comfortable with that idea yet. (Serious counseling you know)

    In October 1983 I looked at this truck on the dealer’s lot then decided not to buy it well about two weeks later I decided to buy the truck but when I went back to the dealer it was gone an older couple had bought the truck to retire on pulling a fifth wheel across country then in December the old man got sick and passed away so his wife put the truck and fifth wheel trailer up for sale on the lot where they bought the trailer.
    Make a long story short I seen the truck go up for sale in February 1984 and bought it. I ran the truck hard real hard working, fishing and just in places you wouldn’t think it would fit but did then in 1996 from the ground up I rebuilt the truck with all GM parts. Now in 2007 it’s time to once again give my buddy a facelift and some fresh parts.

    I don’t know how to explain it really but to me that truck is just like a pet is to others, we’ve been through alot together.


    American Zombie’s idea of replacing the odometers might work if I can get the needle off without breaking it so I may try that in a few days.
     
  9. gonaads

    gonaads Beware the G-Man Political User Folding Team

    bush dogg, the only thing you can do in situations such as this is to either get a new replacement Speedo/Odometer and have the Dealer give you (or it will come with) the sticker that needs to be attached to the speedo housing showing that said speedo was replaced and the sticker would have date and mileage of when it was replaced. Cracking open a speedo is not a good idea. The rollers that have all the numbers on then will never ever line up exactly the same again. (It's kinda like what Perris posted as to the wheels) If you have ever seen a car/truck where the mileage window has the numbers and they look uneven (in other words they don't line up in a nice flat straight line), the speedo has probably been opened. Your best bet is to get the speedo, install it, make sure the speedo cable is installed correctly to the speedo head and then... Now for the fun part, get under yer truck, disconnect the speedo cable from the trans and get yourself a reversible drill. Make sure it's a high speed or at least a normal speed drill. The slower speed ones are no good for what you are about to do. Now that you have the speedo cable disconnected from the trans place the nub or end of the cable into the chuck of the drill. Do not place the cable housing in with it, only the actual cable nothing else. Now for best results use and electric drill. Reason I say this is that some may have access to air tools. Now get someone else to visually look at the speedo and pull the trigger on the drill. If the speedo starts running at some MPH then you got it going in the correct direction. If the speedo needle is just sitting there kinda bouncing a bit then you have to set the drill in the opposite direction (this is the reason for a reversible drill). Now the best drill would be one that has a locking trigger. This way you can just let it run. Now in order to know how long this will take to get 63,000 more miles on your new used speedo run the drill for a couple of minutes or up to 5 minutes. Write down the mileage before you do this then take note of the mileage that has clocked off in the time you have run. Then you can guage how long it will take. Don't run the drill non-stop or you could burn it out. Run it 10 minutes at a time with a couple of minutes rest between.

    Now the only other way to do this if ya don't want to have all this exciting fun :p is to take your new used speedo to a speedo shop. Have them set it to the correct mileage. And since you wish to raise the mileage and not lower it they shouldn't think you are trying to tamper with it for some shadey sales thing. Now I don't know how much it would cost you to take it to a speedo shop, but it's the easy way to do it. Unless you feel like having some fun and you have time on your hands to do it the power drill way.

    Good luck. :D

    Oh yeah, the nice thing about these older trucks is it's quite simple to remove the speedo cable from the trans. So hooking up the drill should be very straight forward. Let us know what you deside to do and how it all turned out.
     
    Last edited: Mar 19, 2007
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  10. What Gonaads said. Mine stopped temporarily because the worm gear jumped - I made an educated guess at where it would be and just ran it forward using a drill.
     
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  11. bush dogg

    bush dogg OSNN Senior Addict Political User

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    American Zombie;
    Looks like the odometer can be replaced if a person needs too, I took the face off the replacement and it seems you can remove the screws and the odometer just slides out.

    gonaads;
    I thought about the drill but with 60,000 plus mile to go I wasn’t looking forward to it and hoped for something quick and easy.

    But I have fixed this now so all I have is just some minor tweaking left.

    This was something else…all I can do is shake my head when I think about it, when this started the speedometer at time would make a little whine or rattle and the needle would jump some “very rare but maybe once every few weeks to a month” then the speedometer stopped working.

    I was thinking the head right off because of the above symptoms so when it quit I disconnected the cable from the transmission and the back of the head to check the square ends of the cable, they were fine so I connected the cable back to the head and grabbed a person to watch the needle as I spun the cable from under the truck with my fingers just to see what happened “last thing before I decided it was the head as I was thinking”.

    Well the one I will call that person “my mom” said “No it’s not moving” so I was done and ordered a replacement head well when it came in I took the dash apart to get the old head out and also take a look at the odometer…well just for grins I thought “I’m giving her one last spin before I pitch this thing… the damn thing went to 50mph? it works” so I left the old head in and put the dash back together.

    With more trouble shooting I left the cable disconnected from the head pulled out from under the dash and went for a drive “I felt circular movement with my thumb from the inter cable so “the problem well what was the problem? At this point start over”
    I checked the head myself again, then replaced the cable and the speedometer still didn’t work so I moved to the transmission I pulled the speedo bullet from the side and found that the plastic gear inside the transmission was messed up, the speedo bullet was acting up and when it would catch it would round the square hole some inside the plastic gear so after time this square hole became round.
    I replaced the plastic gear inside the transmission, left the speedo bullet off and connected the cable direct at that point the speedometer worked fine so I’m on the downhill side now.

    But there was one last thing to do “ask mom” about the speedometer not working when she was watching it? So I did.

    Me…hey mom remember when you watched to see if the speedometer moved for me?
    Her reply…yes I do it would only go too 20mph I think and stop so it was broke. “Not quite what mom told me that day”

    :laugh: :laugh: :laugh:

    Now keep in mind I’m under the truck turning the cable with my fingers. :laugh:
     
  12. gonaads

    gonaads Beware the G-Man Political User Folding Team

    Heh heh, you know that was one of my thoughts, as to maybe the speedo drive gear at the trans could have been worn out. But the way your original post was I figured that wasn't an issue so I didn't bring it up. :s Well, it seems you found and fixed the problem. :D
     
  13. bush dogg

    bush dogg OSNN Senior Addict Political User

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    Yep my original post was biased, I had pretty much made my mind up that it was the speedometer head before I even checked anything out.

    I thought transmission for about one second then said nope can’t be that transmission it’s only three years old, But what I didn’t think about is the speedo bullet on the outside with it being steel with a steel pin that goes into the plastic gear inside the transmission.

    I should have jumped in with both feet and really checked it out more thoroughly but I didn’t really want to mess with it that day and get too greasy but at the same time the odometer not working messed with my head so… I had hoped for the easy clean quick fix and ran with that. :)
     
  14. gonaads

    gonaads Beware the G-Man Political User Folding Team

    One thing though, if the trans is only 3 years old then you should really check the gear and it's housing down at the trans. Look to see that there is no undue wear in the housing where the plastic gear sits and also that it is not binding. Also look for any excessive in 'n out movement. This could cause the gear to bind and help it to wear out prematurely.

    Now one other thing I was thinking is if you had the trans replaced rebuilt or whatever the reason for it being only 3 years old, then it is possible that when the trans was installed they (whoever put the trans in) used the same old speedo gear. It could have been a bit worn and then got worse. Maybe.
     
  15. bush dogg

    bush dogg OSNN Senior Addict Political User

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    That’s a good idea checking the housing where the gear seats in the transmission on the back side “I checked for unusual movement” but I didn’t think to use a flash light to peek in that hole too look around at the other side…so I think I’ll take it apart again Tuesday or Wednesday to check on that, I bought a new plastic gear from GM and don’t want it messed up prematurely, granted it was only $7.00 but still worth a look.

    I had the transmission rebuilt 3 years ago and it’s very possible that gear wasn’t replaced “I would hope the shop replaced it but hard to say” because at that time the transmission had about 100,000 miles on it 4th transmission rebuild “I’m hard on them and this shop knows that”.

    I looked the old gear over for what that’s worth and it didn’t tell me anything really as to if it had been replaced at the rebuild and with the constant heat and fluid on it all the time I just can’t say for sure.