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paul44965

Drilling and tapping a hydro-gear

paul44965
12 years ago

After reading several posts about hydro-gear transmission problems I figure I need to drain replace the transmission fluid. I have a Craftsman mower (Model #971.27680) with a Hydro-Gear transmission (Model #356-0510). I plan on carefully drilling and tapping the transmission and replacing the fluid through the top vent hole. My question is what is best to use as a plug? The transmission appears to be cast aluminum. Will any material work, steel for instance? Or due to heating and expansion should I only use an aluminum plug (if such exists)? Any help any of you can give would be great - several of you have given great help in the past. Also, any thoughts as to the best place to tap?

Paul

Comments (7)

  • justalurker
    12 years ago

    You don't want to use like metals.

    I would go to the local Yamaha or Honda dealer and look at drain plugs for smaller motorcycles.

    Generally coarse thread and large wrench size with a magnetic insert to catch filings. They usually use a crush washer to seal.

    Best place to drill and tap is harder to decide unless you have the tranny out and disassembled. The thicker the casting where you drill the better. AVOID thin areas. If you drill the wrong area it can be a very costly lesson.

    There might be two cavities you want to drain... diff and pump areas.

  • mownie
    12 years ago

    Seems like you are missing a digit in the 917 number. And I have been unable to get anywhere using your 356-0510 number either.
    I favor using a brass plug having an internal hex tool provision (Allen socket). For best results, just drill and tap for a "1/8" NPT plug", nothing larger. That diameter will give you the best results (most threads) in the rather thin aluminum case.
    Does this axle have a spin-on filter? If so, you better realize that where you put your drill had better not intersect with an oil passage related to the filter or you might end up with a hole in a pressurized spot.
    I really can't recommend that anybody simply make a guess about where to add a drain hole without having the 2 halves of the case actually separated so you can see where it is safe to drill, and where to avoid drilling.

  • exmar zone 7, SE Ohio
    12 years ago

    I knew someone who was in a similar situation and was determned to add a drain to a hydro where none existed. Just the idea scared me, I finally convinced him not to do it. As I recall, he pulled the trans and disassembled enough to get the oil out or just flipped it over and drained through the vent. Don't remember exactly as it was quite a while ago. Admittedly, pulling a tranny isn't the easies thing to do, but compared to drilling in the wrong spot and creating a "boat anchor....."

    Another consideration would be contamination from the aluminum chaff when the drill breaks thrugh, not to mention the tapping. And it is aluminum so a magnet isn't going to do much if that gets into the trans fluid.

    just my very humble opinion,

    good luck,

    Ev

  • bingopin
    12 years ago

    I would wonder if the casing is thick enough to accept a plug. Typically there is a "boss" or thicker section cast into the housing at the location of drain plugs or other tapped holes.

  • paul44965
    Original Author
    12 years ago

    You are correct Mownie, I left off a digit on my model number - it is 917.276801. The Hydro-gear model number is 400506. 356-0510 is a cross reference number. If I decide to remove the trany and crack it open, where can I find a new gasket for it? Thanks.

  • mownie
    12 years ago

    No gasket! It requires a good grade of sealant only. Preferably the same type of sealant used to assemble aluminum motorcycle engine/tranny cases. It is a different compound than typical silicone RTV sealant. But I suppose RTV might work OK if you get the kind that is formulated for aluminum surfaces.

  • exmar zone 7, SE Ohio
    12 years ago

    I'd suggest you pose your question at the Craftsman/Sears forum at my tractor forum .com I tried to attach the link, but GW doesn't like it. I also had to space out the address above, just run it together.

    The folks over there eat, sleep, and breathe Sears/Craftsman tractors and can probably answer your question immediately.

    Good luck,

    Ev

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