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Transmission crossmember frame nut possibly crossthreaded?


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Were it mine I'd drill right through the body/floor, find the drill bit sticking out inside the car, then drill a hole big enough to extract the bad nut and insert a new one.  Do the work from above, not below.  Just make sure there's nothing sensitive above before the first drilling operation.

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...Wanting to part out a car for one stripped nut is a bit on the insane side. If this is a big hurdle it might be better to step away for a while.

 

You can buy longer taps. Or tap holders. 

 

Any shop that can weld is going to be able to cut out and replicate the piece. If you are worried about alignment, have them cut it out from the inside of the car, fish out the piece, replace it and weld a patch over the whole thing. You could also take sawzall or something and cut parallel to the floor into the mount, pry it open, drop it out, replace it, then pry it back up and weld it.

 

Tony that tip about shattering a broken tap is golden! Going to have to remember that for next time.

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As NewZed said. Work from above. Use a magnet on a sliding extension rod (Harbor Freight and others-cheap) to hold the nut to get the nut started then use a socket from above to hold the nut as you tighten from below. May require an extra set of hands to either hold the nut from above or the bolt from below. Or...more of a permanent fix - assuming you can clean the nut to metal mating surface JB Weld the nut in place from above. Hold the nut with the magnet making sure you don't get any JB Weld on the threads. Leave the magnet attached until the JB Weld dries then bolt from below. JB Weld may or may not permanently hold the nut but either way you will be able to bolt up the trans mount.

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"I don't want to give up and sell or part out my car. I'veinvestedarrow-10x10.png too much money to let this project go. "

 

CORRECTION:

You SPENT too much. You did not "Invest" anything.

Dighera's Rule of Performance Automotive Ownership:
A car is a hole suspended in midair by four, inedible doughnuts.
Into this hole, you throw buckets of money, which disappear and which you will never see again.

 

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I tapped mine using a standard tap and a 4" crescent wrench to drive it. in fact, since the nut plate 'floats' in there, once I got the tap started i angled it inboard for clearance and was actually tapping into the nut plate about 60 degree angle from the centre of the tunnel. Not straight up from the bottom.

If I wasn't so cheap, I would have bought a proper tap extension to do it with the tap handle.

Then again, with all the 8-point sockets in a Craftsman Set, one fits taps so any ratchet and extension would do the trick...

@Seattlejester, I have been called into shops for broken taps on expensive heads. You want to talk about the look of amazement "Where is the old broken tap?" (Grind-Grind-Grind WHACK!) "Got a Magnet?" Three Guys with wide eyes just dumbfounded they had not considered doing it themselves! LOL 

NOW TO THE ISSUE AT HAND:

 

You have drilled the hole oversize for an M8 bolt. Now you either use the Helicoil tap (which is around an M10) and shoot a helicoil in there using the above suggestions for tap extensions or working in confined spaces, or you get an M10 bolt and put those threads in there and use a bolt one size up.

Why be limited to an M8? You can still tap this as a piece of cake. Do not EVER chuck a tap in a cordless drill. NEVER EVER... That is how you end up with shattered taps stuck in nut plates.

Edited by Tony D
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I did go up in size to an m10 bolt. The previous owner tapped the passenger side to an m10 bolt. I did the driver side first with an m8 size but failed. Now i tried to do the drivers side again with an m10 size but also failed with using the cordless drill. Should i try to attempt to JB weld then drill and tap m10? Or is it not adviseable due to the weight and vibration of the transmission?

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What do you mean by fail? Your descriptive abilities aren't intuitive here. The only thing we can gather is that you didn't break the tap. 

 

Did you try and lift the drill and the drill was too heavy and you failed?

 

Did you try using the drill and the battery died so you failed?

 

When you tried to go in did it twist on you and is now spinning freely so you failed?

 

Did you hit it too hard with the drill and ripped the newly made threads out so you failed? 

 

You have some very very experienced individuals here who can and have offered good advice, but you have been amazingly vague. Post a picture for heaven's sake.

 

I don't know how you plan on getting JB weld to stay in the threaded portion of a captive nut inside a hole. Use a helicoil if you buggered the thread. Or as is probably the case since you would have to remove it to helicoil it properly, make a new piece once you remove it. 

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I think the OP is psyched out and assuming that this is a difficult job and he will fail.  Hence the blanket "I failed" statements, with no details.  Needs to change his mindset and assume that he will succeed.

 

The JB Weld might be used to hold the nut in place so that he can use his drill and tap more easily.  Apparently the nut is moving around causing him problems.  So a dab or two of JB Weld to hold the nut might help out.

 

Get the right holder for your tap or make up your own.  Getting the tap started straight is your problem here.  Trying to use a bulky cordless drill as a handle won't work.  Guys that do much tapping probably use their fingers and a tight grip to start the tap, then a wrench to carefully advance it.  You have to be very aware of how you're twisting the tap, no side loads, just rotation.  It's difficult if you haven't done a few.  

 

One trick you can use to make a tap handle extension, if the tap is the right size, is to use a socket upside down, with an Allen wrench in the socket where the nut or bolt head would normally be.  The tap goes where the wrench socket drive would normally be.  It works with 1/4" and 1/2" drive taps.  The other odd sizes are more difficult.

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  • 2 weeks later...

UPDATE:  I recently posted a WTB craigslist ad.  This guy responded to my ad says he has a series 1 240z production date 12/70.  He will be cutting it up and offered to sell me the transmission tunnel ears.  He showed me pics and told the threads were in good condition.  No rust around the ears.  I just have to go and pick them up in Sacramento Area.  I was thinking of having a shop just remove the old ones and weld in the new ones since I have no welding experience.

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You could just take a hole saw and cut a circular piece out.  Seems like you're overthinking the problem.  I'd take it to a body shop and let them recommend a fix.  They're used to working with sheet metal and structural elements.  It's not complicated for somebody who works in the field.

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You're just planning way too much cutting and welding.  Cut a 2x2" piece out and weld in a new one.  They can even fabricate a new floating nut.  Or cut the floating nut piece out of the parts you've bought or are planning to buy if you just have to have original Nissan parts.

 

Find a friend who has some real mechanical skills who can look at it and give advice.  If you go in to the wrong shop with this problem they're going to milk you for hundreds or thousands of dollars when they realize that you don't know much.  Only being blunt to save you some money and future problems but you're on the verge of making a big mistake.  This would not even be considered a real problem for most of the people on this forum, just a simple activity, maybe an hour's worth of time.

 

No offense.  You're in over your head.  You're on the right forum though, if you can just take the advice.

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Very much so, a shop that can weld is not necessarily a shop that you want to have weld. Booger welds and stuff can be hidden easily under a coat of paint to a brief glance and seam sealer can hide a lot of sins. You won't know it fails until your trans is dragging on the floor. You are also planning on doing a butt load of work. 

 

New zed's advice is golden, you are on the right forum, you are being given very good advice, it is up to you to heed it. This would be a very simple job for someone who is mechanically inclined to replace the nut/plate that is inside via several methods mentioned, that is if you did really mess up the threads which you still haven't really told us how you "failed." It would be even easier for someone to tap in new threads assuming you didn't fail in the wrong way.

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So you essentially drilled out the hole with an oversized tap. That indeed does not bode well, but that does clear things up and does give you options depending on what you want to do.

 

You can still save it if you wanted. You can drill it even bigger, and carefully manually tap new threads into it and then use a thread shrinker to bring it down to more normal size. It looks like a grub screw, gets screwed in with a flat head and has threads on the inside. 

 

This would be an example:

http://www.sweetwater.com/store/detail/KM21500?adpos=1o3&creative=54989489041&device=c&matchtype=&network=g&gclid=CMWe3pHEt84CFQdafgodS6sJMQ

 

Or you can use any of the other methods mentioned. 

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