Comanche Rear Bumper Bolt Size?

[DirtyJeepGuy]

Hey! Got a 86 Comanche. I pulled the rear bolts off it and mis placed it. Its the ones that go along the frame and have nuts welded inside the frame. Trying to mount my JCR rear bumper and completely lost the bolts. Anyone know the size?

[Strokermjcomanche]

M10x1.5 don't know the length though .

[Megadan]

You can estimate the length with a bit of coat hanger wire.  Just put it through the hold and out the nut at least the width of the threads and mark the other side where it meets the frame.  That should get you close.

[DirtyJeepGuy]

How hard would it be to bust the weld nut from the inside and slap a upgraded nut and bolt in it? Note the bed is off my comanche. So its all accessible.

[87Warrior]

When I went to install my JCR rear bumper on the 86, most of the weld nut inside the frame broke off. I decided to break the others off with an air hammer and long chisel attachment I had. Easy to do and I retrieved the broken nuts with a magnet. I upgraded to Grade 8 bolts with a large washer and a lock washer through the frame (from the inside). Nuts are now on the outside with a lock washer. It is a little tight with the JCR bumper, but I could still fit a breaker bar and socket inside the frame to hold the bolt heads so I could torque down on the nuts. Seems to be holding tight with nothing coming loose after pulling a trailer nearly 300 miles. I did this with the bed still bolted to the truck.

[Eagle]

How hard would it be to bust the weld nut from the inside and slap a upgraded nut and bolt in it? Note the bed is off my comanche. So its all accessible.

Slapping an "upgraded" bolt in the hole, secured by a loose nut, is not an "upgrade." With a weld nut in the frame, all load on the bolt is transferred into the nut, from which the welds distribute it more or less uniformly over a large-ish (relatively) area of the frame. If all you have is a bolt and a loose nut, forces from the bolt are transferred directly to the frame at the point where the bolt shank contacts the hole. Less than half the circumference is actually positioned to resist forces in any particular direction, so it probably won't take long for the hole to become elongated. Once that process starts, how do you stop it?

 

Of course, if the weld nuts bust loose in trying to remove the bolts, you have no choice. But I certainly wouldn't recommend intentionally breaking them loose.

 

The factory bolts for the rear bumper are a lot longer than they need to be. 25mm should be plenty long enough, and 20mm would probably do the job nicely.