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Frame Stretch


mattb73lt

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I was looking for some imput on how to best do a frame stretch.

I have a fairly short wheel base 1960 B-73LT(L cab) and am going to stretch it into a car carrier for my antique cars. What I have for a body is a late 70's Jerr Dan roll back that was mounted to a Ford truck. I saved everything from the Ford from the cab back and it's all still mounted to the frame.

The Mack frame is about an inch shallower than the Ford frame and the outside measurements are about 1/4" less than the inside measurements on Ford frame. This would allow the two frames to slide together and by placing two 1/8" shims down the length of the joined areas, take up the difference.

I was thinking about doing the stretch in this manner, then using body bound bolts, bolt the whole thing together using the cross member patterns and a logical bolt pattern in-between for maximum strength.

The reasons for method were to simplify and speed up the mounting of the body, since it's already mounted to the frame and to create a double frame for more strength due to the increased wheelbase.

The dimensions of the two frames are so close to allow this. Once alligned,squared and joined, I would use all Mack components for the drive line.

In theory, it would seem the best way to proceed, but I'm also thinking safety and not creating something dangerous. Also, if I ever sold it, it would be very easy to separate and return to it's original configuration if so desired by the new owner, leaving the frame very unmolested.

Looking for some thoughts and possible alternate methods?

Thanks, Matt

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Yeah, that's what I had in mind. Much longer wheelbase,though, due to the body length. I was going to demount the body, blast,prime and trim/repair the donor frame. Repair the B-73 frame, as it had tandems installed at one time, then mate the whole thing together as you did and remount the body to complete it.

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  • 2 weeks later...

Yeah, that's what I had in mind. Much longer wheelbase,though, due to the body length. I was going to demount the body, blast,prime and trim/repair the donor frame. Repair the B-73 frame, as it had tandems installed at one time, then mate the whole thing together as you did and remount the body to complete it.

With a much longer frame and use of a roll off(high center of gravity when in use) I would recommend "z" cut, stagger joints, and weld (SMAW-ROD NOT MIG) the existing frame rails to desired length. Then slip an inner frame to the whole length bolted to the outer extended frame. Always bolt together inner and outer rails with grade 8 fine tread nuts and bolts. just my .02 cents

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