Differential Fill Plug removal. Help...

[TravZ]

New to owning a Z. Previous owner had the car for about 10 years, and didn't do a ton of maintenance. Like change trans, diff fluids. I got done with the trans and went to do the rear end.

 

Its a 73 240z.

 

Male square headed bolt is the fill plug. I torched it, penetrating fluid. Torched it more. The only thing that I can get on there is a standard adjustable crescent wrench.

 

Is there a better tool? Do I need to remove the rear crossmember to have better access to it? If so, does anyone have a good step by step with pictures or a video on how to drop the crossbeam? 

What about  filling through the breather? Is that a check valve / one way valve? Or is it an empty tube? I took the cap off and am fairly certain I felt something inside of it that would make filling through it tough.

 

Anyways, please help before I round the head of this bolt off. 

I don't have a welder, by the way... so if I need to weld something to it to get a better grip, it's not the best option for me at this time.

 

Thanks!!

 

 

[NewZed]

The nuts for the cross piece are hard to get to.  But removing it will give you more room to work.

 

Buy a bigger wrench if you need to.  A pipe wrench will also work.  It will chew it up the plug in a different way than just rounding the corners.  But, used properly, it will self-tighten as you apply leverage.  They only go on one way.

 

Heat the aluminum around the plug, not the plug itself.  Aluminum expands more than steel with heat.

 

Use big leverage.  Get your wrench set up in the proper place so that you can get a long cheater pipe on the end and will have room to move it.  Heat the cover around the plug and apply leverage while it's still hot.  Aluminum conducts heat very fast also so the time you take putting away the torch and getting set to apply leverage can let it tighten up again.

 

If you can, using your leg to move the wrench or with a friend, apply the force while you heat the cover.  That way you'll use the minimum amount of heat needed to get it to move.

 

Just some tips.  Your problem is not uncommon.  Getting things setup just right before applying the heat and the force is important.  It's all of the halfway attempts beforehand that tear things up.