Replacing skid nut within frame?

Well now I've gone and done it... While removing my front skid this morning one of the screws fought me all the way out. Had to break out the impact wrench. Luckily it backed out, but now the nut within the frame crossmember is loose. The screw when reinserted can wiggle back and forth suggesting that the front tack weld on the nut is broken.

There's no real way to access the nut within the frame, other than cutting the frame. What's the best way replace this nut with something secure enough for the skid?

I'm thinking to drill out the affected area with a hole saw, then machine a cylinder of steel of that OD with a tapped hole in the center, then weld it flush to the frame.

Are there any better options?



I've got some surface rust there but this is an overwhelmingly rust-free socal truck.

 

I think I'd try a rivnut in there before your labor intensive approach OP.

A conventional nut on the back of the bolt would be much better of course but (imo) it seems the great majority of the skid forces will be in the up direction (or lateral) vs pulling down on the skid (so the weaker rivnut may suffice.) The size rivnut will matter of course.. my cheapo Wetols rivnut kit off of Amazon was only $40 but the largest size is 3/8". You might want a 1/2" rivnut?

EDIT: Sorry OP, I believe you are saying you can't get the bolt out because the nut is spinning. My apologies. Perhaps take Key-Rei approach below.

 

I had this happen, I wouldn't drill it out if the threads themselves are still good, mine were.

What I did was use a flap disc to remove paint all the way around the welded in frame nut to see the extent of the crack around the threaded insert in the frame and have a clean surface for weld. I then took my Dremel with a small round carbide burr bit and traced the crack and about 3/8" beyond it about halfway through the frame, pre heated the area to 275°F with my MAP torch and then ran a bead of GMAW in the excavation. Let it fully cool to the touch slowly and then careful with a very fine abrasive pad on my die grinder brought the raised pass down to flush before painting and running a tap through the threads.

Haven't had an issue since.

 

Thanks guys! It sounds like my understanding might be off.

I was assuming there's a nut welded to the inner surface of this frame crossmember, behind a hole that's sized for the screw. I'm imagining it being tacked in two or three locations, and based on the play I see when I reinsert the skid screw and wiggle it around, all but one of those tacks have now failed. So basically I have an inaccessible nut inside a tube, on the brink of spinning freely.

But based on what you wrote, it sounds like it is actually some sort of insert nut. In other words it's not entirely behind the frame, but flush with it. If that's the case I could definitely excavate around its perimeter and re-weld it. That's welcome news.

I'm not sure what went wrong today, I pull the skid regularly and this is an antisiezed stainless steel bolt. But for whatever reason I had to beat the everlasting piss out of it with a 1000+ fuggadugga lithium-ion bolt stripper. First time I've really unleashed the thing for more than a second or two--usually a brief jolt is enough to either break anything loose, or at least shear off the head.

But this bolt wanted a fight today, all the way out at full power for many seconds, never turning freely. Surprisingly the threads are mostly ok. Looks like I could get away with retapping the nut, so long as it's secure to the frame.

 

For what it's worth the torque on those bolts is only like 30ft lbs.

 

Well thats a good point... I've probably been overdoing it for years. But never had trouble backing them out until today. It broke loose as easy as the others with my socket. But kept getting harder. I was straining with a 2-foot cheater before I decided to break out the impact. Expected to see galled up threads when I got the bolt out, but nope, threads freely into other holes. The nut isn't quite free threading but isn't destroyed either, I am ordering a tap to clean it up.

Thanks again.

 

I ain’t about to use a Torque wrench on those bolt. Lol
Hand tight is good enough.

I don’t even live in a rust prone state and the threads on mine were rusted.

OP is lucky the bolt didn’t break off coming out. Those bolts are about as “strong” as the oil and trans pan bolts.
They are prone to breaking clean off.

 

I was able to tap mine out to a slightly larger thread and has held well. That said it its totally gone, you can drill it out and have someone weld something like this:

$19 Allstar Performance ALL18550 3/8"-16 Weld-On Nut, (Pack of 4)

Amazon.com: Allstar Performance ALL18550 3/8"-16 Weld-On Nut, (Pack of 4) : Automotive

 

And fwiw, I always make sure these have anti-seize.

 

I got a “threaded handle”. Used a 3/8” bolt. Cast iron, zink plated. Fits in the frame the handle stops it from spinning. Simple fix

 

I like the way you think, are you sure it can handle 30ftlbs. j/k

 

Yeah I don't use the torque wrench on them either but the point being a lot of people seem to think they need the bajebus torqued out of them when they really don't need much more than a firm snug.

 

At least. Its been holding my skid on for about 2 years.

 

I made sure to apply anti-seize to mine early on after I first removed them. Ever since then they thread in & out like butter anytime I remove/install the skid plate(s).

 

Hey guys, thought I'd post an update. I finally fixed this (hopefully!)

In this case, it turned out that the nut wasn't directly welded to the frame. It's welded to a piece of sheet steel, and that is welded to the frame (from within). That piece is maybe a couple inches long, and ends near the nut. (I could only tell by feel, sticking my finger through a nearby drainage hole in the frame, so I'm not really sure what the actual situation is). In any case, when I was wiggling the bolt up and down, that piece of metal was bending up and down within the frame, held by the remaining weld on the far (inboard) end, but clearly having broken loose on the short (outboard) end near the nut.

The likely reason for the failure is that my frame is slowly bending inwards there due to frequent use of the skid. But hey, I like driving over rocks. Another possible reason might have been the bolt binding against the skid during removal, forcing the nut upwards. My skid mounting holes don't line up perfectly any more -- it's always a pain to get them all started, and at least one fights me to tighten them up. Again, I like driving over rocks, so these things aren't unexpected.

I posted a summary of the repair (with pictures!) on the welding thread:

I'm not sure if it's a permanent repair, but it's at least solid for now. And the good news is that, based on what I perceive about the design of this captive skid nut assembly, even if all the welds to the frame fail, the long-ish piece of sheet metal to which the nut is attached can't spin freely -- it will hit the frame, allowing removal of the bolt (so long as the threads don't gall up on me.)

So for sure I'll be re-applying antiseize from here on out!

Also as mentioned above, I slightly enlarged the clearance holes in my skid to hopefully avoid binding during installation and removal. Only like 6 more projects to go before I am ready to reinstall the skid to find out.

Thanks everyone for tuning in! I'll post again if this fails.

 

I'll also add that I preemptively replaced the majority of the bolts in my frame, including these, with stainless hardware a couple years ago. Slightly increased risk of galling there, but they are super strong and don't rust. (And galling wasn't the problem here.) Downside is that most of them have 1mm larger head size, so instead of needing 10, 12, 15mm... wrenches, I need 11, 13, 16... But I don't think I'll ever shear off a bolt head again, especially after witnessing what this bolt survived completely intact.

I too live in a state where rust usually isn't a problem, but I have developed an affinity for driving to salty places. Like death valley for example. Careening across salt flats will completely coat your truck with salt dust! So even though I've never driven down a slushy salted roadway, I have to be super proactive about rust prevention. Cleaned and painted the whole frame, drivetrain, suspension, etc. with POR15 a couple years ago. Here's what was lurking above the front skid despite a thorough rinse-down after the last trip:



It's not as bad as it looks, most of that is just caked dust. But the white dots are salt crystals!

Worth it; death valley is awesome.

 

I really need to do this sooner than later... the rear crossmember bolts are spinning freely on the front skidplate for my CBI skids.. and I really need to remove them to scuff and sand it all,repaint the skid, and prep the underbody for a slathering of woolwax.. I also want to enlarge a few holes, add a few drain holes & bend back the front skids mount tabs (middle ones bent on a hard hit)...