So I have a 2004 G35 coupe, I was trying to replace my transmission pan and I was having trouble getting it off because the bolts were very rusted and 3-4 of them broke off. I had no other option but to drill them and try to extract them and in the process of doing that I think I may have made the holes bigger on the bolts I had to drill out and extract. I only say that because when I put the new pan up the oil was leaking a bit. Is there anything I can do to fix this ? Will I have to put in bigger bolts in?

 

You don't necessarily need larger bolts. Helicoils might be a possible solution. Essentially, you drill and tap the hole to a larger size thread, then thread in a stainless insert into the aluminum. These allow you to re-use the original size/thread pitch bolts, and its often stronger than the original threads were.
I think those bolts are M6x1.0mm threads. I've used this kit on dirt bikes in the past and had great luck:
https://www.rockymountainatvmc.com/p...d-repair-kit-p

As I remember, its very thin aluminum around the pan, so if you go this route or another, you'll need to be careful. You might be able to drill/tap to another size, but it makes it a pain having mismatched hardware, plus you'd have to drill out the trans pan bolt holes.