I have a '66 custom cab lwb styleside, what I have been wanting to do is shorten the truck 12". I am working in a carport with a gravel floor. Is there a way to do this right without building a frame jig and striping down the whole truck. Can I do this by clamping channel iron to the frame to align it before welding? Any Ideas?
Kris

 

Well, you do want the body off the frame, so you can move the frame sections around easier. It's much easier to align, clamp and weld a 500 lb frame than it is to align, clamp and weld two halves of a 4500lb pickup

If you have the truck down to the frame, then cut, you could probably do this on plywood using multiple adjustable jacks, which could be bottle jacks, hydraulic jacks, or even screw jacks (machinist jacks). You are going to need something to align the sections of frame because you want the two sections level and square before you weld anything so you can align the front end later, and get the body mounts to line up properly for reassembly.

You might consider going through your circle of friends, and see if any of them have a flat driveway or garage floor they can loan you for a period of time.

I've extended trucks before, using two pieces of C-Channel per side. I've sized the c-channel so that a larger piece slips on the OUTSIDE Of the frame rail, and a slightly smaller piece slip son the INSIDE of the frame rail, then weld it all together then seal, prime and paint. Added about 20" to an old crewcab that way. Took quite a while to line things up properly before I even bothered to pull the welder out of the garage.

 

Depending on where you want to cut out the section, I believe you could find a way to tack some possible l_l (turn this upside down onto the frame) shaped pieces to either side of the section that hold a piece of metal in place that keeps the frame aligned. Obviously, you can not have much play in between the pieces. Do some studying about the proper locations to weld on a frame. There are area's on the rounded edge of the frame that are weakened by welding. A combination of welding and bolting, huck bolting if possible is always prefered. Do not make a straight line cut thru the frame if possible. It is sort of an L shaped cut that you make on either part, that will give you the best strength. The nice thing about doing this on bigger trucks if that you can just roll the axle forward many times and burn off the back. I am doing a Hino at my shop right now, rolled the axle forward several feet, I must have 12 feet of spare frame hanging off the back now. The shops order them long, as a roll is much less expensive to do as compared to a stretch. Some truck manufacturers even make the driveshaft sections match up to popular cab to axle lengths so that you can just remove a section.

 

Along with the excellent information offered above, I would suggest using a "saws-all" with a metal cutting blade to do the cutting. They are extremely accurate, and a "z" cut on the frame is said to be stronger than a straight vertical cut, although I think a welded straight cut with a gusset plate bolted on the inside of the frame web is more than adequate, especially in 1/2 ton trucks. I'm no expert though, so this is just an opinion.