Stripped gearbox drain plug

[surfstar]

The drain plug on my gearbox is stripped, and it being a large/weird size I'm not sure if the auto store will have a next size up self tapping plug. The bolt head is 23mm - its huge - but I'm sure the threads are more like 12mm or something. Googling around I found a rubber compression plug, similar to what I use in the transom of my boat, as you tighten it the rubber expands outward creating the seal. web page

Do you guys think this will work for a gearbox plug? If I do get the thing to plug up and not leak, I don't plan on changing the fluid for a couple years, and would probably use a suction pump to not have to remove the drain plug. I've also read of an oversize self-tapping plug with a new smaller plug in the middle that you use for draining, haven't seen any, though.

 

[andyd]

Ive used the second type you mentioned for stripped out oilpan plugs. Try a NAPA parts store.

 

[cousincletus]

How bad are the threads on the unit itself? You may be able to chase the threads with a tap and replace with a new drainplug.

 

[labman]

I ran a rubber plug from JC Whitney for years that sort of streched into the crankcase of my Valiant.

 

[surfstar]

I went with the rubber expansion plug in 5/8" and it seems to be working so far. Auto stores didn't have the size of the old bolt in the computer so I wouldn't know what size tap or oversize bolt to get and the piggyback bolts in the store were SAE and not metric. Simplist solution for me was this. Will be checking for leaks for a while to be sure.

I was able to re-use all my old oil, as I hadn't lost enough to need any makeup oil and it is only about 5k miles old. I filtered it with a coffee filter to be safe - boy did that take a while.

 

[cousincletus]

Was the plug specifically designed for an oil pan? Because if not, the rubber may not be the correct type and may deteriorate in oil.

 

[surfstar]

its designed for oil pans (made by Oil-Tite) and is a one time use thing, so when i change my gear oil i'll need another one. or i could just siphon/pump it out of the fill plug in the future. don't see any leaks so far.