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Cross threaded seat mount nut

rampage

rampage

3/4 ton status
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I’m replacing my buddy’s floor mat in his ‘84 truck. Had to remove the front two seat mounting bolts to get the mat under the seat and found out the the genius who replaced the carpet cross threaded the bolts that hold the seat to the floor. :surepal: I’m guessing he used a power tool and didn’t start them by hand. Looks like my options to repair it are limited since the captive nuts are both inaccessible because it has gas tanks on either side. So it looks like I have two ways to go. First is to try to run a tap through them to clean them up. Which type of tap is best to do this - taper, plug or bottoming tap? Second is to use a Heli-coil.
Any tips or other options or is that about it? Dropping the tanks and re-welding the cage is above my pay scale.
 
I would think a tapered tap for the same reason. Going to be a tough one either way. For a seat if it all fails I think I would re-tap the next size and not worry about the helicoil unless you already have the right kit. Those things have become expensive.
 
HankScorpio said:
I would think a tapered tap for the same reason. Going to be a tough one either way. For a seat if it all fails I think I would re-tap the next size and not worry about the helicoil unless you already have the right kit. Those things have become expensive.
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I was figuring tapered would be the best but thought I’d get other’s opinions since it’s a one shot deal. Didn’t want to take a chance of making new threads instead of trying to grab the old ones. Hopefully I can repair them.

Price is not a concern since this truck is pretty pristine. Besides, he already ordered new bolts. Hate fixing other people f-ups, especially when they were trying to save a couple minutes instead of starting them by hand. :angry1:
 
The nut were interference or locking originally, and metric.
Probably have some kind of thread locking compound stuck in the threads.
Good cleaning with a wire pipe brush, plenty of tapping fluid
 
Are they really metric? I haven’t checked them yet. If they are then I’m SOL. :doah:

This is the best pic I could get. My camera won’t focus in on them too well but you can see where they’re shiny where the threads are all boogered up.

1724171686582.jpeg
 
My seat mounts bolts in the '85 Blazer are all 3/8-16.

In this scenario, I would not hesitate to drill up to 7/16 and get new bolts. You only need to do that to the messed up ones anyway. My worry about retapping to 3/8 would be the remaining strength of obviously weakened threads.
 
definitely want to chase those threads too. Pretty sure gmt400 is all metric

Sorry for some reason I read 94 in your first post. Yes they are probably 3/8 16
 
Wes Harden said:
definitely want to chase those threads too. Pretty sure gmt400 is all metric

Sorry for some reason I read 94 in your first post. Yes they are probably 3/8 16
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I’ll have to see how they hold when I tighten them down after chasing them to know if there’s enough good thread left. The front bolts don’t really do much except keep the seat from flopping up and down. The rear bolt are vertical so they’re the ones that keep the seat from flying forward and I haven’t removed them yet so don’t know their condition. 4 new bolts are on their way so no need to fix the old ones.
 
rampage said:
I’ll have to see how they hold when I tighten them down after chasing them to know if there’s enough good thread left. The front bolts don’t really do much except keep the seat from flopping up and down. The rear bolt are vertical so they’re the ones that keep the seat from flying forward and I haven’t removed them yet so don’t know their condition. 4 new bolts are on their way so no need to fix the old ones.
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Technically, the seat belts do all the work in an accident. Without a belt, you fly off the seat and the bolts only need to hold the empty seat in place.
 
As long as I’m on the subject of the seat, did it ever come with a latch that keeps the back in place or does it just flop forward to allow access behind it? I thought the ‘78 I use to have had a latch on it. :dunno:
 
rampage said:
As long as I’m on the subject of the seat, did it ever come with a latch that keeps the back in place or does it just flop forward to allow access behind it? I thought the ‘78 I use to have had a latch on it. :dunno:
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It should have a latch or be bolted without tilting forward. Sometimes, people will remove two bolts on a fixed seat and make it tilt without a latch. Other times the latch will stick open.
 
In a pick up tilting backwards is not an issue. In a sedan or SUV if the front bolts fail the seat can tip backwards in a rear end collision. I did a number of seat bolt repair under recalls for this issue.
One friend was rear ended in a rent Corsica was rejected out the back window. Pre fed seat belt law
 
Wes Harden said:
In a pick up tilting backwards is not an issue. In a sedan or SUV if the front bolts fail the seat can tip backwards in a rear end collision. I did a number of seat bolt repair under recalls for this issue.
One friend was rear ended in a rent Corsica was rejected out the back window. Pre fed seat belt law
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It doesn’t tilt backwards it just goes forward without operating a latch.
 
kennyw said:
It should have a latch or be bolted without tilting forward. Sometimes, people will remove two bolts on a fixed seat and make it tilt without a latch. Other times the latch will stick open.
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He’s the original owner of this truck and has never removed or modified anything. Says that it has always done this. I did a little research after posting this and it looks like there’s a pendulum that swings forward and locks the back into position during a sudden stop, much like how a ratcheting seatbelt works. Haven’t looked at it yet but any truth to that?
 
I've had probably 3 sets of the fold and slide later-model K5 seats. All of them folded forward with no resistance, unless you try to do it really fast. For the passenger side you just pull the seat back. As it comes forward, the cable releases the slide mechanism and the whole seat slides forward. This is independent of the 2nd set of slides on that seat that sets the normal seat position. None of the mechanisms had any features that looked like they would prevent the seat from folding, except the little pendulum deal.
 
Just for clarity, this is for the bench seat of a truck, not the buckets in a Blazer.

For anyone wanting to know, here’s a link that sort of shows the inertia pendulum located on the bolt that the seat rotates on in the second pic. It swings forward and catches on the teeth of the seat back shown in the first pic.

http://67-72chevytrucks.com/vboard/showthread.php?t=354236
 
On the K5 there is a nut welded onto the floor pan. When removing the bolt the welds on the nut snapped. If you had to you could remove the nut from the floor pan and then weld on a new one.
 
wazzabie said:
On the K5 there is a nut welded onto the floor pan. When removing the bolt the welds on the nut snapped. If you had to you could remove the nut from the floor pan and then weld on a new one.
Click to expand...
1). I don’t weld
2). I’m not dropping the gas tanks that are in the way.

He’d need to have that farmed out if it came to that. Still procrastinating in getting to that fix. It’ll be the last thing I do after everything else that needs to be done.
 
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