Hi all,
Well, I've finally done it. I've pretty much stripped off the filler plug of my '94 Toyota Corolla Manual Transmission beyond repair, and am looking for advice. Here's what I've done so far:
- Thought that this gear oil change would be just as routine as the other few I've done on the same car. I loosened the drain plug first (Mistake #1) and then went to loosen the filler plug. Drain plug came out no problem, I stripped the filler plug with a 12-point combination wrench (Mistake #2.) So now I have a car with no gear oil, and a stripped filler plug.
- Thought that using a 6-point socket might help, so I went out an bought one, but that didn't really work -- the bolt was already too stripped. I hammered on a smaller 6-point socket and tried an impact wrench, hoping to break the bolt free (Mistake #3.) After this, I was left with an almost perfectly round drain plug.
- Now, I consulted google, and found a lot of good ideas. I tried using a dremel tool to cut a slot in the plug to use a flathead screwdriver to get it out. Cut the slot no problem, but couldn't get enough torque. Plus the plug diameter was much larger than the screwdriver, so that didn't help. Tried to use the dremel to cut the head of the plug back to something that resembled a hex bolt (Mistake #4) but that was easier said than done. Another idea was to cut a notch in the side of the bolt and hit it with a screwdriver or chisel (Mistake #5 -- BIG MISTAKE) I thought this was a really good idea, but I managed mangling what was left of the bolt head seemingly beyone repair.
Here's where I am now. I realize that I am going to have to drill. I wanted to avoid drilling because this is the transmission and I didn't want to risk getting ANY metal shavings in there, but this is a risk I'm going to have to take (of course I'll flush the transmission out as best I can when I'm done.) One lucky break that I might have is that the plug (the "bolt" part that actually fits into the case of the transmission -- not the head of the plug) is actually somewhat hollow. There is a 3/8" hole through it from the factory. This means that my dirlling effort will be minimal -- I just have to drill out the head part that is over this hollow part (make sense?) This will also minimize the metal shavings that I have to deal with.
My plan is to drill this out with a 3/8" left-hand drill bit, on the off chance that the drilling action might loosen the plug. From there I have a few options that I'd like some input on:
So, the "bolt" part of the plug actually looks tubular, with 3/8" inner diameter and approx. 1/2" outer diameter. The best course of action (I think) would be to tap the 3/8" hole with a left handed thread, and then thread a left-handed bolt in there and get the plug out that way. Unfortunately, everything that I have read suggests that the pilot hole for tapping should be 75% of the bolt size intended. Therefore, the existing 3/8" hole would be appropriate for a 1/2" bolt, which would be as big as the OD of the bolt part of the plug.
Something else that I thought of would be to use a heli-coil in the 3/8" hole. I'm not sure if they make left-handed thread heli-coils, so what I could do is install the heli-coil and then epoxy a normal right-handed thread bolt in there, let it dry, and then try to loosen the new boll-plug combo.
As a last resort, I know I can drill out the whole shebang and then just repair the threads on the transmission with a heli-coil, but I would like to avoid that, since I think I can make one of these other solutions work, and drilling out the bolt completely would create a maximum amount of metal shavings in the transmission.
Oh yeah, I did consider ezouts, but I have seen too many mixed-reviews on them and I've never used them before, so I don't want to make another mistake and have a broken off ezout in there to make things worsse.
Any insight to help me get out of this mess would be appreciated.
Thanks in advance,
Joe