I've been trying to remove the manual transmission fill bolt but it's starting to round. The metal seems soft (aluminium?), and I'm worried I will really round it off.

I've used, 17mm socket, wrench

and now I'm going to try using some penetrating oil, but I'm not sure what to use next.

I've ordered a new bolt to replace it so damaging this bolt isn't a problem, I just want it out.

I've thought about several options I've read
-hammer in a 16mm socket or wrench or filing down each side of the bolt
-visegrips
-visegrip locking wrench (vise grips made for bolts)
-special bolt out tools
-pipe wrench


Has anyone had experience with these methods?

 

I would go with the vise grips or hammering on a smaller socket first before going out and buying specialty tools and such.

 

Use a 6-point socket instead of a 12-point, I can't see a 6-point rounding off a bolt.

 

tried penetrating oil then went at it with a file to straighten the edges. couldn't get to all sides though.

again with a 6 point socket, my socket wrench started to slip internally (its mechanism) so used a torque wrench. Wouldn't budge, then started to slip off the bolt and rounded partly as it twisted off. Used a visegrip but no luck. wasn't much room for them anyways. The bolt didn't budge. went to the dealership to get some supplies and while i was there they said they would give it a shot. Waited 30 minutes, they said three guys tried and couldn't get it off.

I went to ct and bought exctract-it socket tool. Let's see how this works.


In the mean time, any other ideas?

I'm worried I'll have to take out the tranny and drill it out.

 

Weld a wrench to it and kick it loose, then replace the drain plug.

 

behind the fill bolt flange is an aluminum crush washer, you might be able to use a propane torch to super heat the bolt and washer........then slap a wet rag on it to cool it as fast as possible. thermal shock.
I've seen several of those over tightened like yours, pipe wrench and cheater pipe, you can also grab the 'flange' of the fill bolt with a pipe wrench.
I've even used an air chisel on the flange edge to get them to break loose.
People need to remember the SAE standard/rule of thumb....."tighten to a sharp rise in torque and then 1/6 turn more."
If all else fails and ya can't get the sucker loose, you can take out the speed sensor and refill thru there; pop out an inner joint slightly and when the oil drizzles out the axle seal the trans is full.
Those old '82's only hold about a quart of 10w30 anyway.