Broken Bed Mount Captive Nut - What to do...

Blaze5012 · September 6, 2017

I made a huge mistake this weekend and broke loose a captive nut for one of my bed mounts (the front passenger side bolt). I got in a hurry to get finished and with the last bolt, I am pretty sure I got it cross threaded and was in too much of a hurry and I broke the nut loose. Such a dumb mistake to make, but here I am...

The nut is contained in the square channel cross member under the bed and I seem to have no access to it. Can anyone offer any advice on how to go about fixing this? I am sure this is going to be a big ordeal to fix, but this kind of problem is out of my knowledge for sure.

I know this is often an issue on older trucks with nuts/bolts rusting but I have not been able to find anything about what to do on the newer trucks or how to replace this captive nut. Any help would be appreciated, especially since I have one loose bed mount at the moment (the bolt is holding but only partially in so the bed has some play up and down).

bndawgs · September 6, 2017

I made a huge mistake this weekend and broke loose a captive nut for one of my bed mounts (the front passenger side bolt). I got in a hurry to get finished and with the last bolt, I am pretty sure I got it cross threaded and was in too much of a hurry and I broke the nut loose. Such a dumb mistake to make, but here I am...

The nut is contained in the square channel cross member under the bed and I seem to have no access to it. Can anyone offer any advice on how to go about fixing this? I am sure this is going to be a big ordeal to fix, but this kind of problem is out of my knowledge for sure.

I know this is often an issue on older trucks with nuts/bolts rusting but I have not been able to find anything about what to do on the newer trucks or how to replace this captive nut. Any help would be appreciated, especially since I have one loose bed mount at the moment (the bolt is holding but only partially in so the bed has some play up and down).

hmm, any pictures of what you're dealing with?

diyer2 · September 6, 2017

Drill it out/remove and replace with standard bolt and nut?

2017_whitez71 · September 6, 2017

Could you drill a larger hole next to the existing hole and use a spring nut or u nut?

Thomcat · September 6, 2017

What you need is a Riv-nut.

Works like a huge poprivet,. but contains internal threads for installing a machine screw or bolt. Dealers use them all the time for installing accessories in blind hoiles in the body....running boards in a unit body SUV, roof racks without removing the headliner, spoilers on trunk without access on the inside, etc. Dealers have a special installation tool to make it easier, but it can be easily duplicated using a threaded bolt and spacer, usually provided with the GM accessory.

Find a Riv-nut that matches the size hole, insert it, expand it with a socket working on the installation bolt against a wrench on the hex spacer sandwiched between the bolt head and top of the Riv-nut, remove the expansion bolt and spacer and install the matching bolt. You have a permanent waterproof install and the bold can be removed and reinstalled while the Riv-nut remains captive.

Blaze5012 · September 6, 2017

Here is a photo of the bed mount. The bolt is sticking out about a half inch or so and just spins in both directions using a wrench.

I can't use a standard nut because it will spin. The spring nut could work if I can get it in there.

Maybe I am missing how the rivnut works but how does it keep from spinning?

2017_whitez71 · September 6, 2017

What you need is a Riv-nut.

Works like a huge poprivet,. but contains internal threads for installing a machine screw or bolt. Dealers use them all the time for installing accessories in blind hoiles in the body....running boards in a unit body SUV, roof racks without removing the headliner, spoilers on trunk without access on the inside, etc. Dealers have a special installation tool to make it easier, but it can be easily duplicated using a threaded bolt and spacer, usually provided with the GM accessory.

Find a Riv-nut that matches the size hole, insert it, expand it with a socket working on the installation bolt against a wrench on the hex spacer sandwiched between the bolt head and top of the Riv-nut, remove the expansion bolt and spacer and install the matching bolt. You have a permanent waterproof install and the bold can be removed and reinstalled while the Riv-nut remains captive.

Never seen such a thing. That's a lot better than my idea. OP looks like this is the way to go.

Thomcat · September 7, 2017

Here is a photo of the bed mount. The bolt is sticking out about a half inch or so and just spins in both directions using a wrench.

I can't use a standard nut because it will spin. The spring nut could work if I can get it in there.

Maybe I am missing how the rivnut works but how does it keep from spinning?

My .02 on this particular install - Easiest way might be to hold the existing bolt head with a wrench, saw off the bolt and push it into the hole, Then remove the spacer giving you access to the hole. The install a riv-nut and since you have limited clearance and can't use a socket, work around the side of the flange installing the riv-nut compression spacer and installation bolt using two box wrenches. The riv-nut works something like a moly installed in a drywall. The riv-nut is placed into the hole, as you hold the installation spacer (a hollow hex with a hole larger than the bolt) captive with one wrench and tighten the bolt with another wrench, the installation spacer presses against the head of the riv-nut so it doesn't rotate in the hole, but the pressure from the bolt which rotates on the top of the spacer, pulls the threaded portion on the bottom end of the riv-nut on the blind side of the hole causing it to mushroom upwards and become permanently wedged in the hole. Then unscrew the installation bolt and what remains is a threaded riv-nut installed in the hole. Then just re-install the spacer and and get a new installation nut with threads fits the threads in the riv not.

Of course there is always the quick and dirty method which sounds nasty, but does work. Used it once on bolt with a welded nut broke loose a friend's set of Honda running boards and at 3+ years it is still holding. Leave the existing bolt. Get a few washers with a center hole a little larger than the shaft of the bolt. Cut a notch in each of the washers slightly smaller than the shaft of the bolt. Then tap each of the washers onto the shaft using a small hammer. Each washer will reduce the amount needed to secure a tight bolt......and the final washer will pull the captive nut tight against the bed. Done. You can always close the notches further with a large vice grip if your worried about the washers eventually loosening, or use metal weld or gorilla glue or something else on the washers.........can always be removed and starting from scratch at a later date.

Thomcat · September 7, 2017

Never seen such a thing. That's a lot better than my idea. OP looks like this is the way to go.

That one in the picture was a spare that came from the GM OEM anthracite running board on my Traverse.

Blaze5012 · September 9, 2017

Thanks for the rivnut recommendation, I had never heard of this either. Hoping to get around to trying this out sometime soon, but Ill post an update after I do