towing a car backwards q:

Discussion in 'The Club House' started by bobski, Jan 11, 2013.

  1. bobski

    bobski Well-Known Member Sponsor

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    will the speedometer cable snap being run backwards with the needle being forced on zero the whole trip?
    it shouldnt whenever you back up, but what keeps it from putting pressure on the needle in the wrong direction?
     
  2. orangello

    orangello New Member

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    That is an interesting question. Back-in-the-day speedos were so simple; my VW beetle had a cable that attached to the front driver's side wheel that ran the speedo.
     

  3. JSStryker

    JSStryker New Member

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    Would depend on the age of the vehicle being towed, most modern vehicles use an electronic input (Hall Effect sensor (?)) for the speedometer these days.
     
  4. danf_fl

    danf_fl Retired Supporter

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    Just disconnect the cable from the transmission.
     
  5. c3shooter

    c3shooter Administrator Staff Member

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    So- if you drive in reverse, does your odometer go backwards?

    Most have some sort of one-way drive. And today they are electronic for the most part.



    Say, if I drove backwards, do you suppose my gas tank would fill itself???
     
  6. Rick1967

    Rick1967 Well-Known Member

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    Actually they used to...way back when. I learned that in high school auto shop. The teacher remembered when they did because he and his buddy put a car up on jack stands in the driveway and ran it in reverse to for a couple of days before he sold it. But by the time I was old enough it didnt do it anymore.
     
  7. trip286

    trip286 New Member

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    My first truck was a '65 F100. Straight six 300, three on the tree.
    I learned how to drive really good in reverse by trying this trick, turning the odo backwards. Didn't work. Original transmission, 1970 motor.

    But, when my little ranger was rear ended, the body shop told me that they were actually able to tell how many times the odo had rolled over 100k miles. They said it had flipped 4 times, and applauded me on keeping the crappiest motor on the road... on the road for that long.
     
  8. Rick1967

    Rick1967 Well-Known Member

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    I was talking about cars from the 30s and 40s. I am 45. My teacher was probably in his fifties. He told us about when he bought a new car that was the first automatic transmission.
     
  9. danf_fl

    danf_fl Retired Supporter

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    I know that if I drive my Hybrid Civid backwards, the speedometer does display how fast I am going.
    I never tried backing any distance to see if odometer reverses.
    (But if it does, I'm going drive backwards before I sell it.)
     
  10. Billy9mm

    Billy9mm Member Supporter

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    Trip I noticed you used the term "three on the tree" that one I haven't heard in a long time. My first car was a 59 Desoto with push button automatic, then came the 64 Comet with 6 banger and three on the tree. Both were back in 1970.
     
  11. blucoondawg

    blucoondawg New Member

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    I wouldn't say the straight six 300 was a crappy motor, look at the mileage they put on, they are just about indestructible. May not be the best gas mileage or power but their dependability is second to none.
     
  12. Vikingdad

    Vikingdad New Member

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    The modern cars with the electronic speedos (even if they have a needle they are still electronically driven) will show the speed regardless of whether you are going in forward or reverse, but the odometer will not go backwards- it will continue to advance! The Hall effect sensor on the transmission cannot tell which direction it is going.

    Older ones, as far back as 1940, operate off of a magnetic drive, so running them backwards puts no strain on anything. I have a couple of 1940's Jeeps and I have taken apart the speedometers trying to get them to stop "pulsing", so I have had them apart and seen how they work. As far as I know all of the earliest speedos used this magnetic drive so you should be good to go.

    What year car are we talking about?
     
  13. kfox75

    kfox75 Well-Known Member Supporter

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    I would have to agree with this. I have never scraped an F 150 with a 300 that had a bad motor. I've scaped 2 with bad transmissions, and 1 with a bad frame, but the motors were put into other trucks which had over 275,000 miles on them. My '92 just hit 215,000 and it runs like it is brand new. Granted, I'm on clutch #3, and have had to replace both gas tanks, most of the brake lines, The wiper motor, the starter (twice), and the front seat (don't ask. I'm still having nightmares!), but it still runs and handles like it was new.

    I will admit that I work the truck harder than a teenager with a rental car. I tow and haul with it constantly, (it's rare that it leaves the driveway empty), but I am a maintenance freak and I have the reciepts to prove it. It would not suprise me if the truck is still going at 300k, I have a friend with one that just hit 385k. I don't give him good odds on 400k, but that is due to it's lack of floorboards. Gotta love life in the rust belt.
     
  14. bluez

    bluez Well-Known Member

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    I wouldnt worry so much about the speedo but your transmission.

    nearly all automativ transmission cars will need you to disconnect the driveshaft even if you put the car in neutral.

    otherwise the Tranny will spin w/o getting lubrication from the ATF pump (which is on only when the engine is on)
     
  15. John_Deer

    John_Deer New Member

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    Once you get the car on the towing rack take the battery cable off the battery if you are concerned. Given that cars are towed backwards every day I seriously doubt it's going to harm the speedometer
     
  16. bobski

    bobski Well-Known Member Sponsor

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    im going to tow a 76 c-10 backwards.
     
  17. levelcross

    levelcross New Member

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    With a 76 C-10 unless it is a K series (4 x 4) then towing it backwards will not be a problem since it is rear wheel drive. As someone else said towing a newer car will eat up a transmission due to lack of fluid flow on most vehicles.
     
  18. ellis36

    ellis36 Well-Known Member Supporter

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    Viking is correct. Before computers and such the speedometer consisted of the speedometer cable from the transmission turning a magnetic disc in the speedometer head. A metal cup mounted in bearings, with the indicator needle attached and a hairspring to provide resistance to the spinning disc was mounted over the magnetic disc. The faster the disc rotated, the further clockwise the disc…and needle were deflected.

    There was also a small worm gear inside the head coupled directly to the cable that turned the odometer gear.
    That said, yes..driving in reverse would decrease the odometer reading. But since the coupling to the speedometer isn't mechanical, it's not going to damage anything in reverse.

    I would figure a '76 has this type of speedometer.

    I would be more concerned about the stress on the differential gears from driving the driveshaft…and the output bearing in the transmission. IMO, when the driving force is coming from the wheels the wear patterns of all the drive components are disturbed. I would probably drop the driveshaft for extended towing.
     
  19. bobski

    bobski Well-Known Member Sponsor

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  20. bobski

    bobski Well-Known Member Sponsor

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    so, lets turn it around and tow it nose first on a classic bumper tow bar instead.
    im pulling a 1/2 ton truck with all 4 on the road with a 3/4 ton truck with a 2" ball. any hidden woes?