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Transmission crossmember frame nut possibly crossthreaded?


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1971 240z with 280z motor. I just finished swapping my motor and tranny into the car. I think I accidently cross threaded the frame nut for the tranny crossmember. What could I possibly do to resolve this issue?

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The floating nut is square so it doesn't rotate. Start the tap once it grabs you can rethread it. 

 

If that doesn't work you are going to have to get at the nut (I am guessing either a nut on a plate or a thread piece of plate), remove it, and put in a new one. If you look from the inside on the trans tunnel you can see where the spot welds are. You can cut a bit of it out and try to fish it out, or you can drill out the spot welds and have someone weld it back in for you after you replace the nut.

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It's funny how someone repeats the same question over because he doesn't like the answer he's been given.

 

I retapped mine EXACTLY as JC suggested and had no issues with the "floating nut"... What is the big problem here? Why can't you do this?

 

As seattlejester suggests above, get the tap started straight and once it grabs you're home free. This is not rocket science.

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That's a shame.  You'll be parting the car out now?  Failed in how to use a tap?  Broke the tap off in the nut?  The nut turned with the tap?  Used the wrong thread pitch?

 

Just kidding.  You're not really asking a question anyway, just reporting a result.

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...

 

If you broke the tap in the nut the shop is going to have to cut into the car to extract the whole plate and replace it. They would need a metric tap and dye set, an angle grinder, a welder, metal stock, and a drill press.

 

That is going to require a very different shop from if you just don't know how to use a tap. 

 

This is also going to cost you a bit to tow the car since driving with just one side of the trans cross member is going to stress the crap out of the cross member. You are looking at a very expensive situation. 

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No information, no way to render aid.

 

Broken tap I. That nut plate is NOT a cut and remove issue!

 

Take the tap you broke to a grinder, make a bluntish flat-chisel out of what remains, taper it slightly so the thing is maybe 6-8mm wide with a 2mm wide "chisel" edge...flat and blunt.

 

Put on your safety specs, hold it in a vice grips and put it in the center of the cross of the broken tap....RAP smartly with a 16oz hammer.

 

The broken tap will shatter/break off the cutting flutes and be out of your hair to try again.

 

This takes about 15 minutes including swearing and composing Oneself to the inevitable and grinding the remains into a suitable tool.

 

Throw it in your box, it will come in handy later till you get the feeling of how to properly use a tap and lubricant.

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I did not break the tap. I used a drill with the correct next size 10x1.25 as an extension. Basically made the hole too big without thread. The tap set I have, did not have longer taps. The tool would not have been able to move since the taps are so short. The tool was so short I could not turn by hand. The tool would touch the floor board without me actually centering it. That's why I used an electric cordless drill and try to do slowly.

 

In the end I messed up. Now I regret my actions.

I don't want to give up and sell or part out my car. I've invested too much money to let this project go.

 

Should I just source a parting out series 1 Z car and have the body shop drill out the spot welds on both? Replace the bad ones with the new.

Edited by Stunt
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