Thread size for trans oil level plug?

B

bob in CT

501 Club
Anyone know the thread size of the transmission oil level plug? This detail is not in the parts book.

I am going to have to try to save the hole by tapping it starting on the inside.

Thanks in advance.
Bob
 
It is tapered pipe thread, do not thread from the inside. If you can't recut from the outside, redrill and go next larger size.
 
That is what I was afraid of. The DPO was a bolt snapper and the plug was galled into the case to the point where extractors would not budge it.
I usually have some luck "picking" the threads but nothing wants to separate.

This is going to be one of those jobs where not one thing is easy.....
 
I take it you have drilled the old plug out, if it is a steel plug you may be able to use a torch and get it hot enough to release. Try a couple heat- cool cycles and use a small chisel. Good luck, they can be a real pain.
 
Bob we have the means to make it a 3/8" threaded plug. If you need help let me know. I would also use an allen hex pipe plug. You maybe able to retap it 1/4" NPT and use an allen pipe plug. Some pipe plugs run flush or undersize and some are larger than the others so the'll sit a few threads above the surface. I may have both here.
 
It worked!

I started the original hole just a teeny bit off-center, so I drilled it sideways just a little to center it and then counter sunk the lead-in a little bit and finished it with a 27/64 drill. The tap led right into the original threads. I was lucky. It picked out the remainder of the steel and I extracted a perfect ring from the end of the tap. The plug sits in a little deeper now, but at least I do not have to go oversize.

I would have considered threading in a larger blank and using Loctite, or perhaps braze/silver solder to hold it in. Then drill and tap a new hole the original size to restore the case rather than going oversize.



MERRY CHRISTMAS EVERYONE
 
Bob; Another thought was to weld another larger castiron pipe plug in a larger threaded NPT hole and grind and blend it in so its no seen. Then drill and tap it for the 1/4"NPT pipe plug so its still orginal. Food for thought down the road if anyone else runs into this problem. You can also weld a steel pipe plug to catsiron too with the proper welding rod too.

I'm glad you made out ok.... BB
 
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