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Speedo Correction

Discussion in '40- & 55-Series Tech' started by drohweder, Feb 18, 2004.

  1. drohweder

    drohweder

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    Another active thread prompted this one and I have been driving around with uncorrected speedo since I got the truck. What have you guys used, if anything, to correct the speed given different tire sizes?

    I understand there is a speedo gear in the tranny, where and how I switch it out I don't know...help on that one appreciated. The other question is how much? Is it a worthwile expense. It would be nice to have an accurate speed and odometer. I have also heard there are electronic tachs that hook in like a normal tach and you tell you speed and distance with rear end, tire size as variables. Any luck finding one of these?

    If it would be a quick (one day or so) and inexpensive correction I would love to hear your experiences. Thanks again. D :cheers:
     
  2. Landpimp

    Landpimp

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    I don't know the answer but I have a hairbrain thought........

    as I have been messing with the odo on my fj40 I had a thought, why not just adjust the speedo needle a bit(it pulls of) and this would correct for the difference? it won't fix the odo being off and I am not sure how it would work though the speed range......actaully I am pretty sure it wouldn't work........or would it? na.......that can't work!
     
  3. devo

    devo

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    I live in Denver and we have a speedo shop can take care of you.
    Delux speedo 303 629 6958.
    When I went to 33s and 488s my speedo was way off. They have a gear device that goes between the Toyota speedo gear and the cable that works just fine.
    devo
     
  4. IDave

    IDave

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    SOR sells the gears. 16/17/18/19 teeth. Look up speedometer gears. Number 1 in the figure. It looks pretty simple to me.
     
  5. IDave

    IDave

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    LandPimp,
    Adjusting the speedo needle will make it correct for one particular speed, but since the ratio of revolutions to actual speed is a constant, you will still be off above and below that speed. That is to say, to be "on" at 45 mph, you will have to read "5" at 0 mph and "55" at 60 mph.
     
  6. Archengine

    Archengine

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    Cheap and easy=remove gauge pod, pry up the 6 tabs holding unit together, take apart, paint speedo face with black spray paint, take white paint marker and straight edge, and draw the new speeds where they coincide with your tire size. To determine the new speeds, get a friend in the truck, bring a GPS that tells speed in mph, and while you drive to 10, 20, 30 and so on, according to GPS, have your friend lean over and make an accurate mark on the glass where that speed is. Preferably do this on a quiet straight road though, and be safe. Or just use the GPS to tell speed, or just do as I do and memorize the ratios. My 32 is actually 40 mph, with factory 3.7's and 35 inch tires.
     
  7. drohweder

    drohweder

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    Adjusting the needle won't work, as IDave mentioned its a ratio, as you speed up and wheels spin faster the incremental difference is increased. Painting the gauge is novel but if I did it it would loook like a preschooler got to it. I like the idea of swapping out the speedo gear or just getting a digital tach with chip to do the exact computing for me.

    Any idea on how expensive these new speedo gears are? Do you have to drop the tranny to get at the box? I'd really like to have a stock but accurate gauge if at all possible.

    good input. thanks
     
  8. G_Stratton

    G_Stratton

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    You shouldn't need to drop the trany, but you might have to remove the parking break. At least on an older three speed T-cass you will. ;)
     
  9. Vortec62

    Vortec62

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    I got a ratio adapter for mine. It goes between the t-case and the speedo cable. I took my rig for a 20 mile drive and wrote down how many miles the odometer read for each mile post I went by. This gives a ratio of odomoter miles/actual miles. The longer you drive the more accurate you will be. You send this off to a speedo shop and they put the required gears in the ratio adpater for you. Mine is dead on now.
     
  10. IDave

    IDave

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    [quote author=drohweder link=board=1;threadid=11748;start=msg107322#msg107322 date=1077213919]
    Any idea on how expensive these new speedo gears are? Do you have to drop the tranny to get at the box? [/quote]

    070-01B 1TFR S/D GEAR-1965-8/80 * 16 TEETH 19.94 Yes
    070-01B-U U #1TFR S/D GR-1965-8/80 USED 16 TEETH-No return on Used Parts 9.00 Yes

    070-01C 1TFR S/D GEAR-1965-8/80 * 18 TEETH 25.42 Yes

    070-01C-U U TFR S/D GEAR-1965-8/80 USED 18 TEETH-Availability limited to stock on hand-No return on Used Parts 10.80 Yes

    070-01D 1TFR S/D GEAR-1965-8/80 * 19 TEETH(Discontinued-No longer available) 0.00 No

    070-01E 1TFR S/D GEAR-1965-8/80 * 17 TEETH 22.24 Yes

    070-01E-U U TFR S/D GEAR-1965-8/80 USED 17 TEETH-No return on Used Parts

    As I say, call specter. I think it would be easy and I am virtually certain you don't need to drop the transfer OR remove the parking brake to do it. But the only time I've had mine apart I did happen to have the transfer down on the floor. I think it is a bolt and a metal wedge that hold it in place IIRC. Undo the bolt and pull the mechanism out, change out the gear, stuff it back in and slip in the wedge and bolt down. Done.
     
  11. Landpimp

    Landpimp

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    thats what my brain was trying to tell me.....and it makes PERFECT sense, see I knew it wouldn't work ;)

    [quote author=IDave link=board=1;threadid=11748;start=msg107104#msg107104 date=1077159373]
    LandPimp,
    Adjusting the speedo needle will make it correct for one particular speed, but since the ratio of revolutions to actual speed is a constant, you will still be off above and below that speed. That is to say, to be "on" at 45 mph, you will have to read "5" at 0 mph and "55" at 60 mph.
    [/quote]
     
  12. IDave

    IDave

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    You start losing your hair, and your brain goes next. :-\
     
  13. drohweder

    drohweder

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    Thanks IDave et al. I will order up the part and maybe get it fitted next weekend.
     
  14. Archengine

    Archengine

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    Hey Droh, post up how it went, as I never realized those were out there, and for that price I might be very interested.
     
  15. drohweder

    drohweder

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    Digital Performance Speedometer M9222

    Here is the info on the gauge I was looking at, not the calibration potential. Can run off a mech cable too. Kindof pricey and an extra gauge to clutter up the dash. May try to find a tach, speedo combo with this ability. Brand is NORDSKOG

    • 3 3/8" diameter.
    • Programmable, 300 mph speedometer with LED bar graph, digital readouts, odometer with trip.
    • Easy one button calibration. No screwdriver or pace car necessary.
    • Can be calibrated as many times as necessary for gear ratio and tire size changes.
    • Recalls high speed, 0-60 mph time and 1/4 mile ET.
    • Works with most existing electronic speed sensors.
    • Transmissions equipped with mechanical cables. Requires S9013 Sender.
    • Standard with High Brightness Red display. Green or Amber display is available by adding "G" or "A" to the part number when ordering.
    • $149.99
     
  16. drohweder

    drohweder

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    here is the sender unit, another $60!
     
  17. drohweder

    drohweder

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    Another thing I am thinking about is using a fuel mixture gauge (mounted under the dash) Anyone have experience with these units? Haveing a carbd engine now it seems important to keep it dialed in correctly. Your thoughts.
     
  18. drohweder

    drohweder

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    Just talked to the guys at SOR and he said that the speedo gears are matched sets so adjusting it there will not work as the ratio remains the same. :-\Guess my other options are GPS or some sort of inline converter. Anyone had luck with anything or a I just making a big deal over a little thing ::)

    Here's for trying, :beer:I'll let you know if I find something that works. When it comes down to it I will spend the money on a GPS unit if its going to get expensive!

    :cheers:
     
  19. IDave

    IDave

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    Dang, I was sure that would work. Thanks for letting us know, Dan.