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Thread: Gearbox drain plug threads stripped?

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    Obi Wan
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    Gearbox drain plug threads stripped?

    How can this problem be resolved? Is it possible to use a thread chaser or tap if only the threads at the bottom are ruined?

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    Yoda CJD's Avatar
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    Re: Gearbox drain plug threads stripped?

    The pipe threads are tapered, as is the tap. You can chase the threads with a tap, which increases the size of the hole, but at some point the plug will go too far into the case to seal correctly. All you can do is chase it a bit to clean it up and retry the plug. I have seen inserts at some of the bolt supply stores, but they were not cheap.

    There is always the option of tapping to the next larger thread size. Most Triumph plugs I've run accross are 3/8" pipe, so the next size up would be 1/2" pipe.
    John

    1955 TR2

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    Jedi Warrior
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    Re: Gearbox drain plug threads stripped?

    Harbor Freight sells pipe tap and die set. Could try to re-tap at 3/8 pipe, or go to 1/2 pipe and buy bigger pipe plug. Good luck!
    Regards,
    Bob

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    Re: Gearbox drain plug threads stripped?

    If you are using a TR6 style magnetic tip plug be careful tapping too deep as the plug can go deeper into the hole and contact the cluster gears. I'm surprised that they stripped as you really don't need to tighten the plug all that tight.

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    Yoda
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    Re: Gearbox drain plug threads stripped?

    I am not sure but is there something in the middle, like a metric? That way you would not have to chance cracking the case or something like that by tapping too large. I have had to wrap the treads with that white vinyl tape to stop a leak before.

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    Re: Gearbox drain plug threads stripped?

    Go to your local quick lube. They usually have a good supply of self tapping plugs of all sorts for this problem. They can't afford to send one out that might leak or keep one over the pit all day. This happens with the cast aluminum transfercases more often than you'd think.

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    Yoda CJD's Avatar
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    Re: Gearbox drain plug threads stripped?

    Quote Originally Posted by bnw View Post
    Go to your local quick lube. They usually have a good supply of self tapping plugs of all sorts for this problem. They can't afford to send one out that might leak or keep one over the pit all day. This happens with the cast aluminum transfercases more often than you'd think.
    I hear that! I had a Ford Expedition that came with free oil changes, so I let the dealership do the first oil change. I did the second, and the oil plug was cross threaded. I don't let anybody touch my cars.

    Anyway...lotta good ideas, but I think Karl checked out...
    John

    1955 TR2

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    Obi Wan
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    Re: Gearbox drain plug threads stripped?

    Thanks to all that responded. I'm going to try retapping the drain hole with a 3/8 pipe tap. Maybe I can clean up the existing threads in that manner. Actually it is a TR6 box so I will have to be careful not to run the drain plug too deep as mentioned.it seems to me that there was a magnetic drain plug that was shorter in length than the ones you see now with that longish magnet on the end?

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    Re: Gearbox drain plug threads stripped?

    Good luck on the project. Only thing I may add is to drop a pint of oil into it after finishing and let it set for a while.
    You may be able to catch some of the shavings. The addition of a magnetic plug would also be a good idea.
    Harry

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