1988 toyota corolla ae92 5-speed manual, 125000miles
When removing the fill bolt to check on the trans fluid I stupidly screwed the wrong way, stripped the bolt, and broke off a small piece of the threaded lip on the transmission casing. Now I gotta change the oil anyway due to small metal fragments that may have dropped into the oil. So i plan to JBweld the original fill bolt back, and then drill a hole in the bolt itself, then rethread it so a new and smaller bolt can fit in.
So my question is, since the new fill hole will overflow at a slightly higher level than normal (about 1/4"), will that cause any significant harm when I put in the new oil? Or would it be a better idea to measure how much old oil comes out when I drain it, and then add back the same amount?
Normally not a problem. Due to transmission oil volume being extremely temperature-dependent, transmissions are hardly able to even notice even much larger level deviations than 1/4 inch. If I were you, I would not worry about that.
Thanks for the answer! I guess I am being a little paranoid.