Ok, I've got the boxing plates tacked on, they are square, straight, and true..... to each other, and the outside of the frame......

The crossmember doesn't fit. The gap is 27.5, and the crossmember is 27.25. That's .25 difference, or .125 gap on either side, between each boxing plate and the crossmember.

So, do I start cutting this frame up for scrap, or can I weld in .125 (1/8th) plate, to take up the gap? Is that safe? How far do the "shims" need to extend passed the x-member????

Whiskey. Tango. Foxtrot. If it's not one thing, it's another. I need a break. Fiji sounds nice this time of year....

 

LOL, you are correct, it's always another thing I wish I had a better picture of what you are facing. But, what I can tell you is that someone with a good welding background would be able to put you in business. Most every welding certification test I took had an open root pass (gaps). Is the 27.5 measurement you are referring to the distance between the frame rails? And where are you measuring that from...inside edge to inside edge? Given that you are off only 1/4 of an inch, or 1/8 inch on each side, you really aren't off that much. For right now, center the crossmember, in reference to how the wheels will track, and then see how far you are off. Keep us posted, and don't worry, you are just experiencing the joys of hot rodding

 

I can't see where adding an 1/8" doubler to each boxing plate to take up the difference would be a big deal, but I'd first check with the crossmember's manufacturer to check your measurements to be sure there isn't a problem with the frame. Also check diagonal measurements to be sure the frame is square and the center of the crossmember is indeed in the center of the truck. I would cut the doublers ~ 8" longer than the width of the crossmember then cut each end at an angle so the top is slightly wider than the crossmember to 4" wider than the cross member at the bottom kinda like this: /|____|\ That will be stronger than a straight cut and have a better appearance. I'd also drill a 1/2" or larger hole in the center and plug weld it to the boxing plate.

 

I had to do the exact same thing to make up a 1/4th inch gap on my frame. Not all frames are exactly alike. I just put in two plates on each side to make up the difference.. That way there was no gap.. In fact, the instructions on my kit said that sometimes you may have to do that.

 

If your gap is only 1/4 inch try wrapping a ratchet strap around the frame and pulling it in some. Depending on your existing crossmembers it may not work but would be easy to try. Any more than 1/4 inch I would go with the shim idea.

 

Jker -

1/4" is a piece of cake! I would go the added shims idea, but not the full 1/8" on either side. If you set it up net, you'll just be welding the fillet. That's OK between parallel plates, but less than optimum for the square rig of crossmember and rail. That joint needs a root pas for penetration. Make the shims .090 thick. Fillet weld them to the rails, then root pass the welds to the crossmember, letting the weld penetrate into the gap between rail face and crossmember end. Way strong! You'll be fine.

 

Randy, you lost ME on that one. The issue as I read it is the gap is between the ends of the new crossmember and the boxing plates, how are you welding to the face of the frame?