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  • #16
    They make driveshaft disconnects for the RV people too. No connection to the link.

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    • #17
      I think the biggest problem here is the tailshaft bushing for the driveshaft.
      The extension housing on the transmission has a bronze bushing that
      may not get oil if not engine driven. Bigger trucks do not have this extension
      housing, but rather a flange for the U-joint to bolt, and therefore do not have
      this problem, as the ball bearings in the trans can take it just fine.
      So many know it all's and bad information in this thread.
      So many instances of applying a specific bit on knowledge to a broad spectrum
      where it does not fit. So many instances of Trust me, I know what I am talking
      about. So typical of the guys here. So sad but so predictable.

      -Doozer
      DZER

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      • #18
        Originally posted by Tim Clarke View Post
        The old rule of thumb from my boss at the tow company back in the 70's was: " there's enough residual oil in a manual trans to go across town, but if you're going on the freeway, or farther than 15-20 miles, pull the driveline or use the dolly.

        Willy absolutely has it right. Main drive gear turns the countergear, which meshes with gears for the different speeds. all these turn with the engine when the clutch is engaged The output shaft does not turn until a dog clutch connects a reduction gear with the mainshaft, or, couples the main drive gear with the shaft.. In neutral, you can turn the output, and inside the trans, the only thing moving is the main shaft, and the shift collars/synchro assys. Where the lubrication becomes an issue is often the needle rollers hidden inside the main drive gear, where the spigot on the mainshaft rides.
        Tim has it exactly right. The output shaft has no contact with oil, and relies on the
        mesh between the output gears and counter shaft gears to pump oil through to the needle bearings on
        the output shaft. There are holes drilled for this specific purpose.
        Without the countershaft spinning, the output shaft doesn't get lubed. So eventually, it'll run dry,
        and wipe itself out.

        How long can it go? How lucky do you feel?
        Some people swear they've gone thousands of miles...

        The 'quick fix' is to leave the toad idling in neutral- that spins the countergear and the output gears,
        running lube through them.

        t
        rusting in Seattle

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        • #19
          Diverting the thread just a bit, any of you Midget guys that are interested in rebuilding their front ends, I wrote a how to for the
          technically challenged. It is insultingly simple and is not for the mechanics on here.

          https://www.mikeamick.com/76midget/
          John Titor, when are you.

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          • #20
            If someone was in a jam - (would have to be almost life and death lol)

            and they HAD to tow regardless ------------- best bet would be every 10 miles or so panic stop (as best as you could_ then accelerate immediately after, slosh that transfluid fore and aft as much as possible... best odds of survival anyways...

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            • #21
              Originally posted by SVS View Post
              Less a “procedure” than a “cautionary tale”.

              Ouch!
              In part yes, but towards the bottom of the article they do go over what you're supposed to do to tie a Jeep safely. Funnily enough, you actually aren't supposed to tow with 2 wheels off the ground, it's either flat-tow or trailer

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              • #22
                Ok-my scroll finger got tuckered out before the actual end. Lot of popups to fight through.

                The Cliff notes: Transfer case in neutral NOT 4LO. Transmission in gear if manual, Park if automatic. Jeep engine will grenade at 50,000rpm give or take.

                Author assumes transmission was in first gear to come up with 50k rpm estimate. I think the tires would have just skidded so must be more to the story.

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                • #23
                  Thanks. I've towed it 5 or 10 miles but disconnected the drive shaft for the highway. Looks like I'll continue to do so ​​​​

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                  • #24
                    Originally posted by Doozer View Post
                    I think the biggest problem here is the tailshaft bushing for the driveshaft.
                    The extension housing on the transmission has a bronze bushing that
                    may not get oil if not engine driven. Bigger trucks do not have this extension
                    housing, but rather a flange for the U-joint to bolt, and therefore do not have
                    this problem, as the ball bearings in the trans can take it just fine.
                    So many know it all's and bad information in this thread.
                    So many instances of applying a specific bit on knowledge to a broad spectrum
                    where it does not fit. So many instances of Trust me, I know what I am talking
                    about. So typical of the guys here. So sad but so predictable.

                    -Doozer
                    Like I mentioned previously, it is highly dependent on the design of the transmission in question but as a general rule manual transmissions do not use an oil pump so all oil is generally distributed by splash from the cluster gear mounted to the countershaft. As a rule this part of the transmission is stationary when in neutral and being towed, where the driveshaft is turning the output shaft, the exact opposite of when the engine is running and in neutral, everything now spins and is lubricated but now the output shaft is stationary.

                    This is the reason I cannot advocate towing with the driveshaft disconnected. Much like Tim Clarke noted in his post, internal transmission damage is inevitable when towing long distance.Tim has spent decades servicing HD trucks so I believe he is very qualified to make the statement that he did.

                    These precautions are not so much for short durations as there would likely be enough residual oil left to not do any harm. How long of a tow is too long?
                    Well that's anybody's guess.Do you feel lucky?

                    I would not like to see someone here have to pay for a suggestion that no harm will be done internally. But like I say, it depends on the transmission in question, and although I've had MG Midgets and TR's is the past I did not flat tow or have a look at the internals of those gearboxes so I like to err on the side of caution, always cheaper that way if not always convenient.

                    Regarding bigger truck transmissions, yes they do not have or need a tailshaft housing but they do have an output shaft that is subject to the same constraints and consequences as many smaller ones, internal damage when towed with the drive wheels spinning the output shaft of the transmission.

                    Look at any Eaton/Fuller transmission owners or service manual and it is one of the first precautions listed in bold type.


                    CAUTION
                    When towing the vehicle, the output shaft of the transmission must not be
                    allowed to spin or turn. If the vehicle is towed with the drive wheels still in
                    contact with the road surface, the vehicle axle shafts or driveline must be
                    removed or disconnected.
                    WARNING: Serious internal transmission damage can result from
                    improper vehicle towing.
                    !
                    Last edited by Willy; 01-17-2022, 07:32 PM.
                    Home, down in the valley behind the Red Angus
                    Bad Decisions Make Good Stories​

                    Location: British Columbia

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